In Juno, out December 5, Olivia Thirlby finds out just how nice it is to be the girl who’s not in the middle of all the drama. The 21-year-old actress plays the supportive best friend to pregnant high schooler Juno (Ellen Page). “I enjoyed playing upon the insanity of it all. These two have been friends for a very long time, and Ellen and I shared that,” Thirlby says.

The native New Yorker will play another high schooler on the big screen in March, when she appears with Kate Beckinsale and Sam Rockwell in Snow Angels. Thirlby plays Lila, a band member who helps her crush find love and friendship in the midst of his parents’ divorce.

HUMBLE BEGINNINGS: At 11, Thirlby played an oyster in her middle school’s performance of Alice in Wonderland, but soon realized the girl who played Alice didn’t like her. “She used to glare at me because I knew her lines accidentally from memorizing them during rehearsals,” Thirlby says. “Apparently I was mouthing her lines while she was saying them. I didn’t mean to, but I was just so excited to be in the presence of the lead actress on stage.”

As a senior in college, Thirlby scored the lead opposite David Duchovny in the indie film The Secret. “I always knew I wanted to perform,” she says. “I was a typical drama nerd with the hopes of acting on Broadway someday. But as I got older, I realized if you had a name established in film, it would be easy for you to come back to Broadway because they want stars.”

Thirlby is a self-professed “Shakespeare nut.” “I think he’s the best writer of all time,” she says. “I saw the language and was floored. I needed to stand up and speak the words.” She studied at the American Globe Theatre in New York and the Royal Academy of Dramatic Art in London.

ACTING BUG: In first grade, Thirlby wrote a letter to the head of the school, suggesting the lower school also perform a play rather than “making students wait to reach middle school.”

FASHION PHILOSOPHY: “It all starts with a plaid shirt and can go any direction from there. I like to feel comfortable and wear pieces nobody else will wear.”

HORSE PLAY: Growing up in New York City, Thirlby rode competitively. “I want to be a cowgirl so badly,” she said. “I’m so meant to be a spur-wearing gunslinger chick.”