NEW YORK—Charlize Theron would probably not be the first person to come to mind if one was thinking of casting an all-American girl who never grew up and returned to the place of her greatest success: the small town she ruled when she was in high school. For one thing, Theron’s own childhood was lived in her native South Africa. And one would assume that it wouldn’t be something she would really want to revisit, given that it included the killing of her alcoholic father by her abused mother.

However, she does have some good memories of a youth lived in a rural farming community. She says, in a New York hotel room, that although she didn’t look or act like the mean girl who grows up to write books for teenaged girls in Young Adult, she could relate to the idea of a girl who had too much power for her own good.

“I was a mess in primary school. I experienced a lot of that between the ages of seven to 12, where there was a really popular girl in my school and I was obsessed with her. You would go to jail for that stuff today. I am embarrassed to say this, but I was in tears one day when I couldn’t sit with her. I have issues. Then three weeks ago I was in a fitting and I heard a girl saying, ‘I know Charlene,’ and it was the girl who fucked me up in primary school who now lives a kind of sad life.”

In Young Adult, Theron plays Mavis Gary, a writer of books for and about teenaged girls. Her own life is miserable. She has writer’s block, may not be able to finish the last book of a series, and still broods about her teen years. When she lived in small-town Minnesota, she was the most powerful girl in high school and dated the most popular boy. Years later, she decides to go back to do research for her book, but she also has plans to steal her old boyfriend (Patrick Wilson) away from his wife and child. The movie opens Friday (December 16).

Theron admits that although Mavis throws her old town into turmoil with her antics, she liked the character when she read the script. “I thought the things she did were pretty despicable, but not to where I was disgusted by her. I never had a problem with not liking her. I would love to go and have a beer with her, but I would never let her hang out with my boyfriend. Some people can have all the problems she has and suck the air out of the room. She does, in a way, but it’s funny.

“I know that when I read the script, I liked the idea of a woman dealing with mid-30s issues that women can really relate to. She went through life in a certain way, and she is dealing with problems the way a 16-year-old would deal with them. She says, ‘Don’t you know that love conquers all?’ and here she is at 37 trying to get her life together. So I don’t go for the sympathetic portrayal because I don’t really like that kind of portrayal for myself. Sometimes sympathy can feel like you are trying to victimize someone. I think, more than anything, people just want to be understood.”

Oscar buzz is following Theron again, who is already the winner of an Academy Award for Monster. The complicated, tough-talking Mavis is a character that could serve her well during awards season. She says that the role reminds her more of those played by male movie stars of another generation than anything she has seen played by women in recent years.

“Women are way more conflicted than men. We come from a society where we are comfortable with the Madonna-whore complex, where women are really good hookers and really good mothers but we are not bad hookers and we are not bad mothers and we are nothing in between. I grew up on cinema where guys like Dustin Hoffman and Gene Hackman and Robert De Niro got to play all these interesting and dark characters. I saw a little of myself in all those kinds of struggles and those dark things, but it is rare to see women playing those kinds of honest characters. When people say, ‘It is so brave,’ I say, ‘It really isn’t. It is refreshing, and it is great as an actor to do something so truthful. It is really nice.’ ”

The movie is directed by Jason Reitman, whose first three films—Thank You for Smoking, Juno, and Up in the Air—used humour to lighten social-issue backdrops. The issue here could be mental illness, but Theron says she and Reitman never went that far in their analysis of the Diablo Cody screenplay.

“Jason and I did not talk much about what her issues were. I found that can cloud the pureness of a person being a person. We never really talked about whether she is crazy, or asked, ‘Does she need help?’ It’s obvious that she is completely delusional, but we didn’t want to focus on whether she should do four hours of therapy versus two hours of therapy or what kind of medication she should be on. She is just a beautiful car wreck, and there is no cure for that.”

As for her own popularity in school, she admits that she never had aspirations to be a mean girl. “I wasn’t in the popular crowd; I was kind of obsessed with ballet. I wore nerdy glasses and was as blind as could be and boys don’t really like big, nerdy glasses. I had a massive crush on this guy that this interviewer from Vogue found. This guy did not know that I existed in school, and he said, ‘Tell her the crush was mutual.’ Fuck that. It was so not mutual.

“And then he said: ‘I remember those glasses.’ ”

Watch the trailer for Young Adult.