When it comes down to playing a beloved real life character versus a beloved fictional one, Kristen Stewart declares herself Team Joan over Team Bella. Stewart, who plays Joan Jett in the new biopic “The Runaways,” says she felt a tremendous personal responsibility to capture Jett’s essence.

“Bella’s effect on the world wasn’t necessarily as great as Joan’s, obviously, and I never got to meet Bella,” Stewart said. “It’s completely different. All these people who have an investments in these women, that’s awesome…but when it becomes personal and it’s my responsibility to not destroy, like, what people are going to take from the most important part of my friend’s life… Joan has become really, a really big part. She’s awesome and I really love her. If we hadn’t told the story right, people don’t know the Runaways in our generation. Because they’re going to see them through us, it’s a much different experience than making an original fictional story.”

Speaking of Bella, even though she hasn’t seen “Eclipse,” the third installment of “Twilight” yet, Stewart gives high marks to director David Slade’s style on the film, which will come out this summer. “He’s a very technical director. Very. Very. He’s very thoughtful. I think it’s going to be cool for ‘Twilight,’ like, shotwise. He’s very conceptual. He really, really takes a lot of time to…you’re not going to see, like, a bunch of Steadicam. It’s very deliberate, which is very cool. It gives you more time to think about what you’re doing. I don’t know [the tone] because I haven’t seen the movie.”

On “The Runaways,” Stewart felt an instant connection to Jett, in part because they both experienced stardom from an early age. “We have been professional [from] a young age, which is hard, but her [in] such a different way,” said Stewart during a press roundtable at Sundance for “The Runaways.” “Like the biggest adversity I face is bloggers and [Jett] had people throwing bottles in her face and saying, like, ‘Sit down, you ugly loudmouth.’ To see how assured she is now and that she wasn’t always like that and it actually took a lot… And what she has now is a really, really, really thick armor and you see that happen in the movie. That’s what I wanted to do…She’s a survivor and at the same time she demands to live her life the way she’d like to. She’s a very smart inspiring person.”

Stewart played guitar before filming started, but wasn’t prepared for the rigors of playing in the movie. “We all had two weeks that we had band practice where all of the girls came in. They played the songs that we recorded, I think there was five or six that we had to have done. They played them over a speaker, but then we were like trying to play as a band to it. It’s exhausting, especially with the guitar. I would be exhausted at the end of a rehearsal.. I’d be like, ‘Oh my shoulder is killing me.” So it’s no surprise that even though she sings very capably in the film, Stewart said she had no plans to record her own album.

We’ll have more on “The Runaways” in coming days, including comments from the real Joan Jett.