Emma Roberts: Miss Sunshine

I guess I have too many teeth for my mouth. All the Robertses have these huge teeth,' is Emma Roberts' explanation of the toothy grin that she

Emma made her film debut at the age of nine in the movie Blow, playing Johnny Depp and Penelope Cruz's daughter. Subsequent roles in films such as Nancy Drew, an adaptation of the teen detective novels, Wild Child and Hotel For Dogs have turned her into one of the hottest young talents around. 'But I don't want to get into trouble or ruin things for myself. I feel like an old woman because I like to stay home and read and write and I'm exhausted by about 11pm.'

Her reading list is impressive, ranging from Bret Easton Ellis to Alice Munro to Joan Didion, but in other ways, she seems very much her age. Chatty and open, her mobile never straying far from reach, Emma's conversation is a volley of rat-a-tat responses, and as she lounges in the Andaz West Hollywood hotel in skinny jeans, studded Doc Martens and an Alexander Wang T-shirt, she looks every bit the off-duty LA teen. Her base is in Los Angeles, though she loves London ('The Electric on Portobello does the best eggs Benedict and I'm obsessed with Liberty') and she was back in the UK to make her latest movie, 4.3.2.1.

The film is directed by Noel Clarke, whose films Kidulthood and its follow-up Adulthood have led to him being dubbed one of Britain's rising talents. In it Emma plays Joanne, an American working in a London supermarket. She and her three friends (played by Tamsin Egerton, Ophelia Lovibond and Shanika Warren-Markland) unwittingly become involved in a diamond heist and over three days the girls crisscross London and New York. 'It's a cool action flick with the girls getting to be badass and kick butt,' says Emma. 'There's a lot of chasing and running away from bad guys and comedy, too. It's basically got everything.'

It also has girl-on-girl action: 'Although Shanika was the one doing that, and that was fine by me because sex scenes are always awkward. I did a film recently called What's Wrong with Virginia and I had to do this scene with this guy Harrison Gilbertson. I was 18 at the time and he was 16, and when we were on top of each other, I wasn't allowed to move a muscle because it was illegal.'

4.3.2.1 is one of a slew of films Emma has coming out, including Twelve, featuring Gossip Girl's Chace Crawford and Curtis Jackson, otherwise known as the rapper 50 Cent. 'He's such a sweet, cuddly guy. He looks just like a teddy bear,' she says. The cuddliness of 50 Cent notwithstanding, the film, based on the novel by Nick McDonell, tells a story of violence and drug-taking among the wealthy young Manhattanite set – the Twelve of the title refers to a new designer drug, a cross between cocaine and ecstasy. 'It's always been one of my favourite books,' says Emma. 'There's a lot of sex and drugs, but my character Molly is the moral compass of the movie.'

While her films might depict a hedonistic lifestyle, Emma, by her own admission, isn't 'a hip, going-out person' at all. 'I go out a lot more in London just because I've got more friends there, like Tamsin [Egerton]. I love my passion fruit mojitos at The Electric because I can drink when I'm in London [21 is the legal drinking age in California], but I'm much more of a homebody here in LA. If I was ever photographed falling out of a club, my mum would be outside my apartment in ten minutes, telling me to move back in with her. My family and friends help keep me grounded.'

That Emma seems so level-headed says a great deal about her, given the instability of her formative years. Her mother Kelly and her father, the actor Eric Roberts – Julia's brother – separated when Emma was seven months old, with Julia reportedly taking Kelly's side during the 1993 custody battle. Eric struggled with cocaine addiction, eventually getting clean in the early Nineties, and recently appeared in the TV series Heroes. 'We don't really talk. He lives here, but I don't really see him. I do follow him on Twitter, though, if that counts for anything,' says Emma.

Kelly subsequently married Kelly Nickels, the former bassist with the group LA Guns, who Emma raves about. 'I call him Dad. We've always been close.' The two Kellys have a nine-year-old daughter, Grace: 'My partner in crime. She's so much fun, my friends prefer her to me.'

Emma remains close to her aunt Julia, who leaves a message for her during the interview. 'I'm going to her house on Sunday. I love being with the family because it's so nice and relaxing.' Julia and her husband, cameraman Daniel Moder, have three children: five-year-old twins, Hazel and Phinnaeus, and Henry, who's nearly three. 'She's a great mum and just a really cool lady,' says Emma.

Having grown up around film sets, Emma's choice of career was perhaps inevitable. 'When I was young, I was constantly putting on shows and getting my mum to hold a flashlight on me like a spotlight.' She would often visit her aunt on set. 'The film I remember most is Erin Brockovich [Julia won an Oscar for the title role]. I was on that set a lot and it would be one in the morning and my mum would have to drag me home. Somewhere there's a Polaroid of me trying on all my aunt's padded bras.'

At the age of nine, Emma secured a small role alongside Julia in the 2001 film America's Sweethearts and in the same year auditioned for the part of Johnny Depp's daughter in the film Blow. Based on the true story of American cocaine smuggler George Jung (Depp), Emma played his daughter Kristina Sunshine. 'My mum only let me audition because she thought it would shut me up for a while,' says Emma. 'I had no idea of the film's subject matter and I didn't even realise who Johnny Depp was. He gave me an autographed picture that says: "To Emma – one of the most beautiful people I've ever met" and it's a really hot picture of him on the beach in a white buttoned-down shirt. My friends think that I made it myself.'