Twilight star Kristen Stewart ' />

She might have ousted Miley Cyrus from her mystifying position as the World's Most Famous Teenage Girl but 19-year-old Twilight star Kristen Stewart is in denial. "People don't really recognise me," she smiles, knowing it sounds unhinged. "I think I just look different in person or something. I'm also not very approachable." She laughs hard and knowingly.

Take the outfit she wore to the Teen Choice Awards earlier this year (where she won Best Actress Drama for Twilight): a Rock & Republic dress, the skirt section of which comprised only silver spikes. It didn't take an expert to deduce the message: "Don't stand so close to me."

Stewart has already earned a reputation in the media for being difficult, but it seems a rather uncharitable label. In my meetings with her, she has been fidgety, yes, uncomfortable, check, awkward, always, but never rude, dismissive or arrogant.

"I do feel that nowadays everyone perceives you the same way," she says, pondering a Facebook/Twitter age in which she does not participate.

"I prefer something I can touch! But now everybody knows everything about you. Even your parents have to know where you are because of course you have a cellphone. They can always reach you. You can't even have a private life away from your family, it's like everything is very hands-on."

But she also says she's far more confident these days as The Twilight Saga: New Moon continues its run at the top of box offices around the world.

"I think I've got a lot more comfortable with talking about myself. I couldn't finish a sentence because I was so concerned about how it was going to sound and I didn't want to come across insincere about something that I really love to do," Stewart says. "I realised that instead or refraining from saying things, I should have said, 'I put my heart and soul into this thing and I love it' instead of the really logical, over-analytical reasons why I love it."

Certainly Stewart likes the choices afforded her by Twilight and is too smart to complain about any downside. "It's easier now to do things I really like, like an independent movie that nobody sees. Now it'll be: 'Oh, let's go see Bella in this stripper movie!' It'll be crazy." She laughs hard, like she's loving it.

The "stripper movie" in question, Welcome to the Rileys - starring The Sopranos' James Gandolfini and last year's surprise Best Actress Academy Award nominee Melissa Leo - is one she terms the "most fruitful life-changing movie experience I've ever had. It was the hardest subject-matter. I play a very broken young girl working in a strip club."

Meanwhile, in Adventureland, which came out earlier this and is now out on DVD, she plays a troubled teen in the 80s, and in another film, The Cake Eaters, which opens here on Thursday, her character has Friedreich's ataxia.

"It's a total deterioration of your muscle control, a very debilitating disease," she explains. "She's just about to be in a wheelchair and is fighting for that last bit of independence from her mother. It's an optimistic, triumphant story."

Next year she will star as Joan Jett in Runaways, based on rock icon Jett's teen girl group.

Stewart started acting at 9 and insists there was "never a grand plan", either to pursue a film career (her parents are both in the business) or to manage it once begun. Her Australian mother Jules is a script supervisor preparing to direct her first film, K-11 (starring Stewart), her father John a TV producer. When a talent scout spotted Stewart in her school's Christmas play, her parents grimaced.

"They said, 'We don't want to be stage-mums'," she recalls.

Her father was particularly dispirited at the prospect. "He was a stage manager then and was like, 'oh my God, I don't want my kid doing this'."

Their contrary pre-teen was having none of it. "My parents were reluctant and I just remembered thinking: 'Actually that might be really cool. I might want to go on a few auditions. I might work."'

She auditioned relentlessly for a year without booking a single job. "It took a really long time until I was totally over it and then came my last audition. I went to it and I didn't even want to. My mum said: 'Well, this is the last one. You don't have to go to any more.' And that was the first movie I got."

The Safety of Objects, released in 2001, starred a veritable Who's Who of leading ladies, including Glenn Close and Patricia Clarkson, who played her character's mother. The following year Stewart won the role of Jodie Foster's daughter in Panic Room, an experience which cemented her belief she was doing the right thing.

"I think being 10-years-old on one of my first movies and spending a month on it with Jodie Foster had an enormous effect on the way I work, probably unbeknownst to me at the time. At least in retrospect, I noticed it. Jodie Foster is the only one who totally shines out in my mind who really taught me a lot."

When she was 12, and working regularly, Stewart left school to be homeschooled by her mother. "I loved it. Independent study is for me." She worked consistently throughout her teens in films from gritty independents like 2004's Undertow opposite Jamie Bell, the Jon Favreau-directed comedy Zathura: A Space Adventure, horror film The Messengers and Sean Penn's Into The Wild.

On film sets now, Stewart - like Twilight co-star Robert Pattinson - is delivered from take to take under a gigantic golf umbrella to deter paparazzi and fans alike. The call-sheet from those sets, the one delivered daily to the cast and crew employed on a film, lists her under a pseudonym. And she cannot set foot in public, particularly with Pattinson, without the event being disseminated in its entirety from teen fan-sites to snarky grown-up publications.

Do she and Pattinson ever compare notes on the Twilight phenomenon? "The funny thing is we haven't really talked about it. Although we can commiserate and be like, 'ugh, it's crazy'."

While Stewart has been distracted by her work, the fans have remained focused on the film and its actors. They've been ravenous to know every small detail. Stewart got a better handle on dealing with all that attention when she stopped trying to be so guarded about what she said.

"I'm always going to keep what's important to me," she says. "People are always gonna want more and I completely understand, considering that we're playing characters that are so coveted by so many people. I get why they want to know more about us and they want us to be together [romantically] and all of that. I just have to sort of not think about it."

Who: Kristen Stewart, actress.

What: New Moon, in cinemas now; The Cake Eaters, opens December 3; Adventureland, out on DVD now.