Kelly Osbourne : Ozzy and Sharon's little girl grows up

The publicist takes me aside as we are about to enter a suite at London's Soho Hotel and, in a stage whisper, briefs me: Kelly isn't well; she didn't sleep a wink last night; she has been vomiting all morning; she had to leave the last interview six or seven times to go to the loo; no, she doesn't want to reschedule; not swine flu, a dodgy prawn curry, apparently; she's really lovely, but she may be a bit subdued.

Once inside, there's Kelly Osbourne looking tiny and frail, curled up in a ball in the corner of an oversize, puffy sofa. She is wearing a white towelling bathrobe, her shock of peroxide blonde hair slightly askew, a glass of bitter lemon on the table in front of her. Her famously pale complexion – she was nicknamed Casper the Ghost at school – is looking ominously green and, on this evidence, it may not be long before she's off to the bathroom again.

"I feel better now than I did," she says with a groan. "I just wish that instead of throwing up, I got the shits, then maybe I can lose some weight out of my misfortune. It's not fair, but beggars can't be choosers."

So much for subdued. And so much for the idea of Ozzy and Sharon's daughter as a spoilt brat, a trust-fund celebrity scion who has never done a hard day's work in her life. She is many things, she avers, but she's not a flake. "If you look around at girls who are older than me who are children of celebrities, hardly any of them have matured, hardly any of them have grown up to be… I wouldn't say decent human beings, but productive human beings," she says. "They are not bad people; they just don't do anything and I don't want to have a life where I don't have a reason to get out of bed every morning. And a reason to me isn't who I'm having lunch with at Fred Segal."

For someone who is not 25 until next month, Kelly has certainly rattled through an impressive selection of "careers": reality TV star, pop singer, talk-show host, fashion designer, West End showgirl, model and muse and radio DJ. Her latest reason for getting up in the morning, however, may just be the one for which she's most suited. She has just completed a book called Fierce, which is part autobiography but is primarily being billed as a self-help guide for teenage girls (on the title page, she writes: "I would like to dedicate this book to every young woman who's ever felt lost").

Kelly's reinvention as a role model for impressionable teens has, it must be noted, been met with a few raised eyebrows. She was a regular in LA nightclubs from the age of 15; she has lost count of the number of tattoos she has had; she's friends with Kate Moss and Amy Winehouse; and she has just emerged from her third stint in rehab.

And she's not exactly had the most representative of upbringings. Take, as just one example, an episode described in the book as "home waxing a la Sharon", which involved Ma Osbourne straddling her 14-year-old daughter, heating the wax too long and yanking off half her top lip with the congealed yellow guck. Kelly picks up the story: "To make it worse, while I was wriggling around, my mum had pissed on me. She was laughing so hard she couldn't keep the wee in. So as well as burning and scarring me, she also pissed on me."

Come on, that's a bit weird, isn't it? "I remember my first boyfriend; she gave me a police file from the private investigator she had hired to tell me everything he'd been up to. That was my mum, it's just what she does."

But, in the book's defence, Kelly is certainly not short of life experience. She has been diagnosed with dyslexia and attention deficit disorder, and has dealt with two decades of gibes about her weight. She has experienced fame, global acclaim and a pretty hefty backlash. Her mother is addicted to plastic surgery (Kelly's words) and her father has been addicted to just about everything else. Sharon also had colon cancer and Ozzy almost died after a quad bike crash. When you put it like that, is there anything that Kelly Osbourne has not experienced and come through?

The day after Kelly was born in a London hospital in 1984, Ozzy checked himself into rehab for the first time. He held her for a few moments before Sharon told him he needed to go away and learn to "drink like a gentleman". Ozzy turned up for a three-month stint at the Betty Ford Clinic in Palm Springs and, misunderstanding the terms of his admission, asked for a glass of wine. Kelly was spared the most violent stage of his addiction – the one time he approached her, Sharon intervened and hit him over the head with a candlestick – but it still cast a shadow over her formative years. At the age of eight, he sat her down with younger brother Jack and older sister Aimee (who decided not to appear on The Osbournes) and told them: "One of you, if not all of you, will have 'the gene'."

At the time, Kelly had no idea what he was talking about, but it did not take long for her to find out. She could always drink friends under the table, but it emerged that her primary vice would be painkillers – at its worst, she was taking 60 Vicodin tablets a day, "enough to kill any human being". Three rehabs in, she accepted that drugs and alcohol would always be a problem she had to deal with. "They will always be an issue for me until the day I die," she writes in Fierce. "It's all or nothing for me, I'm afraid."

Kelly has been clean since February after leaving the Hazelden clinic – outpatients are called Hazelnuts – and is now cautiously optimistic she can stay that way. "It's probably been the hardest year of my life, this last year," she says. "Every day you get a little bit stronger, but then in some ways you get weaker. Somebody can smoke a joint in front of me and I won't want to do it. Somebody can have a drink and I won't want to do it. But if I see somebody on a plane take a Valium because they want to sleep? I want it. It's like you are grieving it, but at the same time you still find it a bit romantic.

"But they say, 'Play the tape forwards,'" she continues. "If I had one drink, it would turn into 20 and it would turn into drugs, which would turn into puking, which would turn into fighting, which would turn into me being on the front cover of one of the London papers, having to spend the next three months apologising for it. That would be all from me having just one drink."

Her new-found sobriety has led to some fairly hefty changes. Being in America has been fine – no one ever asks why she does not have a drink in her hand; London, however, has been trickier. How does her fiance, 19-year-old Luke Worrall, the so-called "male Agyness Deyn", feel about it? "Luke comes home from work and I'm on the couch into my third book of the day and he's like, 'What happened to you? Is this the same girl I met a year and a half ago?'" she says. "I won't lie and say, 'It's been great!' It's been hard for him because I've been really lost and I depended on him so much that he came home and was like, 'What are you doing? You don't even have anything to bring to the conversation any more, you are just waiting for me to get back.' And he made me realise that I was giving myself my own little pity party – like, 'Boo-hoo, I haven't got any friends anymore because I don't do drugs.'"

Writing the book has at least allowed her, in her mind, some measure of absolution. Ozzy was right: it is in the genes. "You sit there and blame yourself, but it's not my fault. If I had cancer, people would be by my bed going, 'Oh poor thing.' But because it's drugs, it's not socially acceptable. But to me, it's a sickness, it's an illness, a disease; it's not enjoyable by any means. What bugs me the most is that people think I was a party girl and I went around having a great time. I did drugs because I hated myself and I was fucking miserable and I didn't want to think about it any more.

"I think if people understood that, they would start to think of addiction in a different way. Do you really think that Amy Winehouse was in her house smoking crack because it was fun? It was because it was the only thing in her life at that time that she had control over whether she did it or didn't do it. Everyone else told her, 'Get dressed. Go here. Sing this. Do that.' She had no control over anything else except when she did drugs."

By this stage, Kelly is showing few of the ill-effects of last night's prawn curry. She was always the most outspoken of Ozzy and Sharon's kids and there are few dull moments in Fierce. One particularly eye-catching comment comes when she is discussing her weight: "What I've learned through the media is that they look down on someone for being fat far more than for being a junkie," she writes.

"It's true!" she shouts, sitting up and adjusting her dressing gown. "A lot of kids still walk around thinking Pete Doherty is the coolest thing ever. I personally don't get it. Meanwhile, they are writing about how Charlotte Church is disgusting and fat – she's just had a baby! She's not fat!" She's basically screaming now. "But to them it's worse. And it's like, 'Why are you praising Pete Doherty for being a lyrical genius when he's a junkie smackhead and dissing this poor girl who's just had a fucking baby?'"

When The Osbournes was first broadcast in 2002, Kelly was a size 10, but she recalls that attention immediately focused on her weight. Early on, a photograph of her in gossip-rag US Weekly ran with the caption "FAT"; one reviewer made reference to the kids carrying a few pounds – he received a box with shit in it from Sharon with the message: "I've heard you've got an eating disorder? Eat this." In the meantime, Kelly's weight fluctuated between size 6 and size 14, usually depending on what drugs she was taking.

Her lowest moment, however, came during an appearance on Friday Night With Jonathan Ross in May 2005 when she was promoting her second album, Sleeping in the Nothing. "He took a picture of me from my album cover and then another picture of me and goes, 'That's not you, you're fat! Look how much they airbrushed it.' And I just didn't know what to say. You know that feeling where your heart just goes 'BOOM!' in your chest? I wanted to crawl in a hole and die; it got really uncomfortable. The band that was performing was New Order and they refused to play until he apologised. A lot of it wasn't shown on TV because if they saw what he really said to me, I don't think any parent in the world would ever watch his show again. What he said to me destroyed me for two years."

The interview, Kelly says, caused her to sabotage her record deal. "I felt so ugly and fat that I destroyed it," she says. "I thought, 'What the fuck is the point in me doing this shit when a grown man insults me in this way? I'm not strong enough to do this. I'd rather be the trust-fund kid that everyone thinks I am than work my arse off to get insulted.'"

Kelly has no ill-will towards Ross – "I don't feel anything towards him. I don't dislike him in any way, I still watch his show" – but she does regret the demise of her singing. "My music career is, for me, a regret," she says. "I'd never sung in front of anyone when I sang 'Papa Don't Preach' at the MTV movie awards in 2002; it wasn't even something I thought about. But through doing it, I realise that I definitely do have a passion for it: I love singing, I love performing, but I wasn't doing what I wanted to do. I didn't want to be the next Avril Lavigne. It's like, fuck off, that's not me. I want to sing cheesy, gay pop songs, that's what I love."

So there might be a return to singing, but Kelly is also investigating opportunities in TV ("I have about five different production companies telling me that I can invent my own show. What 24-year-old girl is in that position?") and acting ("I got signed to William Morris and they called me in to their acting division and told me, 'You really should do this, trust us'"). Enough anyway to keep her from too many lunches at Fred Segal. Not that she is going to take anything too seriously. "I'm not one of those people that's like, 'I'm a triple threat: I'm a singer, actor and a dancer!' That's not me, I just enjoy it."

For now, Kelly seems content to stay at home and bake Victoria sponges and go to hip-hop/ballet/tap/jazz classes at the gym. She is also, she thinks, probably the only girl her age who still enjoys spending time with her parents. Maybe she is not such a bad role model after all. "When I was 18, I thought I knew everything and I've started to realise that I don't know shit," she says. "But I've been given so many opportunities, I've worked so hard throughout the 10 years I've been doing this now, I will be damned if I fuck it up because of my bad attitude."

Kelly Osbourne: the life

Born Kelly Michelle Lee Osbourne in London, 1984, the middle child of Sharon and Ozzy Osbourne. Grows up between the UK and US as her father tours with Black Sabbath.

2002 Thrust into the limelight on MTV's reality TV series The Osbournes, which runs for three years. Releases debut album Shut Up!

2003 Dropped by Epic Records, signs to Sanctuary and achieves a number one hit covering Black Sabbath's "Changes" with her father.

2004 Launches rock-inspired fashion line Stiletto Killers. It closes in 2006. Goes into rehab for the first time.

2005 Her second album, Sleeping in the Nothing, is generally well reviewed.

2007 Begins hosting reality TV show Project Catwalk for Sky 1. Performs in Chicago in the West End and starts presenting Radio 1's Sunday evening advice show The Surgery.

2008 Becomes engaged to model Luke Worrall.

2009 Third stint in rehab. Releases her teen advice memoir Fierce.

They say "[Kelly is] a wickedly funny, brutally honest, pint-size, potty-mouthed spitfire."
Rolling Stone

She says "I'm an addict. There isn't some fucking magical pill you can take to stop you being that addict."