Who is she? That’s the question that ricocheted around last year’s Sundance Film Festival after Jennifer Lawrence showed up in Winter’s Bone, chillingly raw as a rural teen determined to find her meth-slinging dad and save her family home. Lawrence’s performance, earning her a best-actress Oscar nomination, was both unsentimental and exquisite, nearly convincing us she’d grown up skinning squirrels in the Missouri Ozarks. In fact, since she went without a trace of makeup (except some bloody bruises) and peered out from under a low wool cap, it almost went unnoticed that 20-year-old Lawrence is stunning, with a cherubic, translucent face suggesting a tweeny softness that belies an old-dame brawn and wicked wit rare among Hollywood ingenues.

But Lawrence doesn’t play the ingenue-either on-screen or in life. Before the Oscars (where Natalie Portman won for Black Swan), she joked about practicing her losing face – “I can’t wait to use it. If I win, I won’t be able to!”-without a trace of the faux “it’s an honor just to be nominated” humility that we’ve come to expect from the camera-ready. And wearing a red Calvin Klein tankdress about which the phrase body-conscious would be a riotous understatement, she swears she’d barely begun digesting a cheesesteak when she walked the red carpet. “Fifteen minutes before, the guy doing my hair goes, ‘If you can get a salad, get a salad,’” Lawrence recalls. “I said, ‘I’m getting a Philly cheesesteak.’ I’m sure there’s proof on a hotel bill somewhere.”

It was only for her role as the shape-shifting Mystique in this month’s X-Men First Class-naked save for blue body paint-that Lawrence submitted to a twice-a-day training regimen and a high-protein diet that allowed her to sculpt, yet maintain, her curves. “I knew that if I was going to be naked in front of the world, I wanted to look like a woman and not a prepubescent 13-year-old boy,” Lawrence says, adding, “I’m so sick of people thinking that’s what we’re supposed to look like.”

For a gorgeous movie star with the irritating luck to be discovered at 14 while on a spring-break trip to New York City, Lawrence’s lack of pretense is almost unnerving. In interviews, she accompanies self-deprecating punch lines (“Yeah, that’s how I’m gonna sign my name at, like, the doctor’s office-’Oscar nominee Jennifer Lawrence’”) with full-revolution eye rolls, tossing in Dumb and Dumber quotes whenever possible. Growing up in Kentucky, she was raised by a camp-director mom, a construction-company-owner dad, and two older brothers who never made her feel precious. “Being the youngest and the only girl, I think everyone was so worried about me being a brat that they went in the exact opposite direction of treating me like Cinderella,” Lawrence says. “I’d slap my brother on the arm, and he’d throw me down the stairs. I was always like, ‘Can we talk about excessive force, please?’”

Even when Lawrence is playing vulnerable on-screen, she still exudes a formidable, ever-so-subtle defiance. “She finds strength in every moment,” says Anton Yelchin, with whom she stars in both the Jodie Foster–directed dark comedy The Beaver (as a valedictorian with a painful past) and this fall’s Like Crazy (playing a girl whose boyfriend is pining for his ex). “I’ve watched her do two characters that are different, but they both have Jen in them, which is dignified. Even if they’re broken, they’re never weak.”

With her name now occupying space on every director’s short list, Lawrence was recently picked for the lead in The Hunger Games, based on Suzanne Collins’ postapocalyptic trilogy in which two teenagers are forced to fight to the death-the most coveted part for an actress since The Girl With the Dragon Tattoo. So it looks like the bullied little sis had better get accustomed to star treatment. “When you’re on set, everybody’s like, ‘Oh, do you need water? Here’s 45 bottles!’ It’s really bizarre,” she says. “I’m still getting used to it. I’m still in wonderland.”