Riding shotgun with actress Bel Powley, star of ‘Carrie Pilby,’ on the way to her first Toronto premiere

Ever wondered what it’s like to go behind-the-scenes at a movie premiere? We trailed British star Bel Powley, best known for her captivating turn in 2015’s “Diary of a Teenage Girl,” at last week’s unveiling of her new movie, “Carrie Pilby,” to find out what really happens after the credits start rolling.

“I need a glass of wine,” Bel Powley said, walking out of the theater where her new movie had just premiered. “I asked for water and they were like, ‘It’s a green university, so there’s no plastic.’” She followed a well-heeled crowd out of the auditorium, on the campus of a local school, and clustered backstage with her fellow cast members, exchanging cheek kisses. She thought her new film, the romantic comedy “Carrie Pilby,” had gone over well with the film festival crowd. “People laughed, anyway,” she reasoned.

The skirt on her dress, however, created by British designer Mary Katrantzou, was a bit too long, so she had to keep hiking it up. She did this once more before exiting the building, where a clutch of fans were waiting behind metal barricades to meet her. They greeted her with a smattering of applause.

“Can we do a quick selfie and tweet it out?” a middle-aged woman asked. “I have about four followers.”

Powley obliged and then continued down the red carpet to a waiting SUV. She asked the driver to fold down the seats so she could climb into the last row of the vehicle.

“I’m going to get in the back, like a loser!” she exclaimed. “No one else is going to get back here.”

Her manager and a slew of publicists promoting the film — in which Powley plays a precocious teenager who graduates from Harvard University at 18 only to find trouble adapting to the so-called real world — hopped in the car, too.

“There’s chewing gum back here,” Powley said, taking a piece from an already-opened package. She smoothed out her dress and took a moment to admire it.

“Isn’t it sick?” she asked. “It’s influenced by cowboys and princesses. That’s kind of how I consider myself. Half cowboy and half princess.”

Even though she traveled to umpteen film festivals on the “Diary of a Teenage Girl” press tour, this marked her first visit to the one in Toronto, which traditionally kicks off the awards circuit. “I think it suits Toronto, whatever that means,” she said of “Carrie Pilby,” which is still seeking theatrical distribution. “That’s just something people say.”

After “Diary,” she had trouble settling on a film she wanted to do next. Most of the scripts she was offered required her to play someone especially young, or get naked, like she did in the Marielle Heller film.

“At the beginning, I was just getting sent parts where there’s loads of nudity,” she recalled. “It was like, ‘Oh, she does that. She’ll get her [breasts] out!’”

She liked “Carrie Pilby,” which is based on Caren Lissner’s bestselling 2003 coming-of-age novel, because the character is supposed to be a genius. She liked the idea of saying lines in which she recites the formulas for alcohol compounds. Powley herself, who grew up in London, never attended college.

“I was meant to,” she said. “I was going to go study history and politics. I wanted to be prime minister. And then it just failed.”

She was never a bad student, though. She said she didn’t have a lot of friends in high school because she was so geeky.

“I was really small,” she explained. “I was one of those really small people with a really big rucksack that kind of bobbed along and ate lunch in the library.”

Though she didn’t head off to the ivy-covered grounds of an elite university like Carrie, Powley could relate to the character’s loneliness. At 18, she moved to New York for eight months to do a show on Broadway, and she spent most of it completely on her own, reading and going to museums to fill the time.

She looked out the window of the car, which was idling in traffic.

“Where are we going, though, actually?” she asked one of her representatives, who replied with the name of the place that was hosting the afterparty. She seemed resigned to follow her team’s instructions on where she needed to be. Earlier that day, when she’d started to have her makeup done for the event, she said she just closed her eyes and said, “Literally, do whatever.”

She asked a publicist for her purse and pulled her cellphone out, flipping to Instagram, where she has 18,000 followers.

“I Instagram about women’s stuff,” she said with a smile. “You know, like, women’s stuff? Like power to the women? Feminism?”

She said she would not use her iPhone to Google early reviews of “Carrie Pilby” later that day.

“Damaging stuff,” she insisted. “I just don’t see the point. Sometimes, if someone is really nice, it can be damaging as well. If someone’s like, ‘Oh, she’s really amazing doing this one thing,’ guarantee you’ll never be able to do it again. Nothing’s organic anymore if you start reading what people are saying.”

A minute later, the car pulled up to the party venue. She posed for some pictures on a step-and-repeat, hiked up her skirt again and went inside, where she promptly sidled up to the bar and ordered something clear with three slices of lime.

The room resembled a hip loft and was scarcely decorated, with empty Ciroc vodka bottles lining the windows. She sat on a gray couch next to one of her costars, “Saturday Night Live” cast member Vanessa Bayer, and her boyfriend, Douglas Booth. He had a movie premiering at the festival the following day, “The Limehouse Golem.” The pair met while working on a film about “Frankenstein” author Mary Shelley a few months ago.

The screenwriter of “Carrie Pilby” and her husband joined the couple and told Powley how good they thought her performance was in the movie. They said they liked how she made a character who could have been so bitter and unlikeable somehow endearing.

“I know! Done by a bad actress,” Powley joked, “she could have been really annoying.”

amy.kaufman@latimes.com

Twitter: @AmyKinLA