IT WAS LITTLE MORE than four years ago (September 2007) that Diablo Cody burst onto the movie scene at the Toronto International Film Festival.

She was a screenwriter who, dressed like a kid at a roller rink, didn't look like a screenwriter.

She had a backstory - a former stripper from Minnesota, she was discovered by a producer who loved her blog. She had a cool name. And most importantly, she'd written "Juno," the soon-to-be breakout hit from the film festival that would win Cody an Oscar.

Her next film, "Jennifer's Body," was "not so successful."

"That's kind," she said a few weeks ago at New York City's Ritz-Carlton Hotel on Central Park South.

Now Cody has reteamed with "Juno" director Jason Reitman for "Young Adult," another small-town, character-based comedy, starring Charlize Theron as a slightly unhinged woman who returns to loserville to try to recapture the "magic" she had with her high-school boyfriend . . . who's happily married with a newborn baby.

Sitting down with Cody, who has a 16-month-old child of her own ("he's talking, walking, it's pretty cool"), she's no longer dressed like a kid and is more introspective, except for the full laugh and quick wit.

"My life is dramatically different," she said about her past four years.

"I'm a mother now and I've had some pretty interesting career experiences since 'Juno' - some good, some bad. I think in a lot of ways I've become less accessible than I was then. I was very outgoing at that time of my life and now I feel a little bit more guarded. That about covers it."

She jokingly makes a move to end the interview.

"Originally it was such a novelty to have people interested in me it just felt good to answer questions," she added. "I think everybody fantasizes about being validated on a national scale like that. It was one of those things that was nice to experience, but I wouldn't want to live the rest of my life under close scrutiny or as a public figure. It's not something that appeals to me anymore at all. I just want to write and direct and parent.

"I think I knew and I think Jason also knew that 'Juno' was lightning in a bottle. I don't ever expect to have an experience like that ever again. It was a commercial success; it was a critical success. I won an Oscar. It was pretty intense. So I certainly didn't think I'm just going to do that again, no problem. I wasn't that delusional."

Speaking of delusional, there's Theron's Mavis, the lead of "Young Adult."

"I usually start with a character, and in this case it was Mavis," Cody said. "I think the first scene I envisioned was of a woman freaking out at a christening and causing a scene. I thought that could be fun to write. Eventually, it made its way into the movie.

"Mavis, to me, was the darkest manifestation of a woman who lives in a teenage fantasy, which is something that I've been accused of doing.

"When you first met me I was probably 29 or 30 and wearing a Superman T-shirt and knee socks. That's adolescent behavior in a woman who's pushing 30. So I've been guilty of arrested development myself. In my case it was pretty benign, but I thought, what's the dark side of that? Somebody who can't move on, who can't mature, who's just desperate for attention."

Charlize Theron? Immature? Desperate for attention?

Cody said she was concerned when Reitman told her that the blond South African beauty had been cast.

"It's a hard balance to strike because Charlize is so beautiful," Cody said. "That's something I thought about for sure. Mavis is supposed to be the prettiest girl in school - not the prettiest girl in the entire world. But Charlize is such an amazing actor and so good at transforming herself that she really is haggard in this movie - which she needs to be - and which is cool to see."

So what's next for Cody, a script about motherhood?

"I don't think so," she said. "I find it incredibly inspiring but not on a cinematic level - on a personal level."

Cody does have a completed script for the "Sweet Valley High" adaptation awaiting production ("I can't talk about it. . . . It couldn't be more different than 'Young Adult.' It's '80s, poppy, fun").

But next up, "I'm going to direct in late February. Allegedly. . . . Julianne Hough is the star. She plays this young woman raised in a very conservative home who goes to Vegas. It's a comedy and it's Christmasy and it's nice."