Amanda Seyfried in full bloom

Earlier this week, at an event following the Hollywood premiere of the new movie “Letters to Juliet,” actress Amanda Seyfried found herself under friendly fire. Besieged by back-slapping studio executives and adoring fans — all eager to congratulate her on her role as a young journalist who stumbles into love in Italy — she was pinned down in a restaurant banquette, graciously thanking and hugging admirers as they approached.

But what she really wanted to do was to leave her own party.

“I’m so ready to go,” she sighed while eyeing the next group of people waiting to talk to her. It wasn’t that she was ungrateful for the attention, but rather that she was still rattled after a long day; before the premiere, she had taped an appearance on “The Tonight Show” with Jay Leno, during which she said she had a panic attack. And it was clear that, hours later, she was still feeling anxious.

“I have realized that I hate going to the premieres of the movies that I’m in,” she whispered. “Because I feel this tension after the movie is over that everyone feels obligated to say something nice to you. It’s so unnatural and uncomfortable. You’re not sure if they’re saying it because they feel like they have to or because they genuinely feel that way.”

It’s an emotion that the 24-year-old has had to confront several times in the last few months. After exiting HBO’s hit series “Big Love” after four seasons, she’s appeared in four films since January — “Chloe,” “Dear John,” “Boogie Woogie” and now “Letters to Juliet,” which opened Friday — making her the latest incarnation of a time-tested Hollywood tradition: the “it girl.”

It was only a few years ago that she landed her first small-but-memorable film role as a dumb blond sidekick to Lindsay Lohan in “Mean Girls.” But while Lohan’s career has been tainted by a never-ending stream of salacious tabloid headlines, Seyfried is suddenly being considered a box-office draw. Her last film, “Dear John,” a romantic drama based on a Nicholas Sparks novel costarring Channing Tatum, surprised insiders when it became a modest hit, bringing in more than $94 million worldwide since its release in February. Now, Seyfried’s face is at the center of the campaign for “Letters to Juliet.”

So how has she managed to rise above a pack of other talented young Hollywood starlets?

“She’s drop-dead gorgeous. God gave with those hands for her,” said Mark Waters, who directed her in “Mean Girls.”

But it’s more than her looks that make her unique, says Erik Feig, president of worldwide production and acquisitions for Summit Entertainment — the studio behind “Juliet.” Though he knew casting Seyfried as his leading lady was initially a gamble, he felt that the actress’ combination of innocence, her “naturalistic” approach to acting and her popularity among young audiences made her the right choice.

“She was the one girl on our list who was the most unproven in terms of her box office clout,” he said. “At the time, she hadn’t yet opened a movie like ‘Dear John,’ and even though she was the costar of ‘ Mamma Mia,’ the conventional Hollywood wisdom was that a lot of the success of that movie was due to ABBA and Meryl Streep. But I very firmly believed that Amanda was someone young girls were connecting with. So we took a bet on her. And it was a bet in the fee we paid her — we wanted her to feel like we were making a bet on her, like we were treating her like a star. And I truly believed that she was and is.”

Despite that proclamation, Seyfried isn’t yet entirely comfortable with her new status.

Sipping a cappuccino during an interview earlier this month, she admitted, for example, that she worries about the way she looks. Accordingly, she “throws her money away” by paying $250 for 45-minute sessions three times a week with celebrity trainer Harley Pasternak. And because she speaks often candidly to journalists, sharing tidbits about her life that her handlers might consider too personal (like the fact that she takes the anti-anxiety medication Lexapro), she said that she often has others minding her words.

“Oh, I’m always being briefed by a publicist before I have [interviews],” she said, twirling her braided hair around with her fingers. “They’re like, ‘Come on, you can’t be self-deprecating.’ ”

But that’s just who she is, said Atom Egoyan, who directed “Chloe,” in which Seyfried played a prostitute who becomes entangled in a lesbian romance with a woman played by Julianne Moore.

“She’s very self critical,” Egoyan said. “After I would say cut, she always had this expression of frustration, like she didn’t quite get it. But I found that quite endearing, because she’s always feeling there’s more she can do to capture or enhance or clarify.”

As a young girl growing up in Allentown, Pa., Seyfried first felt a pull to acting after watching Baz Lurhmann’s “Romeo and Juliet.” She began staring at herself in the mirror, she said, reciting lines from her favorite films.

“It was a big deal to me to play characters and feel things and connect to somebody in a fake world,” she said. “It sounds so stupid — a fake world — but I guess, yeah, I just wanted to be those people. To be a part of a glamorous world.”

So she began persuading her parents to allow her to take one-day bus trips to New York City, mostly for television parts. During her senior year in high school, at age 17, she landed a recurring role on “All My Children” and moved to NYC.

Soon, she was accepted to Fordham University. But when she was late to her first English class because of an audition for “Mean Girls,” she began to reconsider going to college.

“I never ended up getting in the elevator,” she said. “I was panicked. It was a big moment for me and I just wasn’t in it. There was nothing in my body telling me to go forward with this. I was like, you know what? It’s fate.”

The move seems to have paid off. This summer, Seyfried will begin shooting Rodrigo García’s “Albert Nobbs,” costarring Glenn Close, and “The Girl With the Red Riding Hood,” which is being directed by Catherine Hardwicke.

True to character, Seyfried still finds the future a worrisome prospect.

“I mean, why am I considered an ‘it girl?’” she asks. “Because I’m in a lot of movies right now or am on the covers of magazines? I just hope there is something solid behind that. Because here’s the thing with ‘it girl’ status. It’s great and amazing that anybody is saying that at all. But how long does that last? I would like to establish myself. I don’t want to just have a moment.”

amy.kaufman@latimes.com