And while It Girls sometimes come and go quickly, in this case, the one in question appears to have real substance.
The 28-year-old U.K.-born Riseborough is no newcomer to the scene. A former member of the National Youth Theater, she studied at the Royal Academy of Dramatic Arts and has shuttled among film, TV and stage roles nearly nonstop ever since: She played a young Margaret Thatcher on the British TV production "Margaret Thatcher: The Long Walk to Finchley," held her own onstage opposite Kenneth Branagh in Chekhov's "Ivanov," and popped up in Mike Leigh's 2008 film "Happy-Go-Lucky."
During the past year, the tempo has accelerated, so she's appearing in three films at the festival: Mark Romanek's "Never Let Me Go," in which she plays Chrissie, one-half of a couple that faces impending death; Nigel Cole's "Made in Dagenham," in which she plays Brenda, a sexually liberated factory worker; and Rowan Joffe's "Brighton Rock," in which she stars opposite Sam Riley as Rose, an innocent waitress who falls for a small-town crook.
The roles are so different -- Rose is starved for affection, and Brenda is an adventurous free spirit -- that audiences might find it difficult to get a fix on the rising star. But that's one reason why she has been so in demand.
"What Andrea has that many actresses of her generation do not have is a bona fide chameleon-like ability to be totally different from part to part," Joffe said.
Riseborough appears to be taking it all in stride. For the past year, she said, she's moved quickly from film to film, "but I always managed a little respite in between each one, so I was able to reset for the next character, which was nice."
She started out playing one of the doomed youth of "Never Let Me Go," a character she describes as "trapped; her whole life is about the preservation of someone else's life."
Meanwhile, Cole was assembling his ensemble of actresses to play factory workers who go on strike at a British Ford plant during the late 1960s. He was struck by Riseborough's performance in the Thatcher movie, "but I didn't think I had a part for her, since the part she ended up playing [in 'Dagenham'], a good-time girl who's screwing around, is so different than that," the director said.
Cole, too, eventually came to realize that Riseborough is "one of those actresses who has an extraordinary physical ability to transform herself." In her first scene she shot for "Dagenham," the moment he saw how she walked across the set, "I knew she'd nailed the character to a T," he said.
In the case of "Brighton," Joffe originally offered the female lead to Carey Mulligan, but when she opted for "Wall Street: Money Never Sleeps" he turned to Riseborough, who, he said, "had always been a very, very close contender."
He credits Riley and Riseborough, playing lovers caught up in a gangland power play, with "succeeding in bringing emotional intensity to material that could have been dry as well as dark."
Now that the films are behind her, she said she is looking forward to talking about them as they're unveiled in Toronto.
"When you're making something, you can't be objective about it at all because you can't pull yourself out of it," she said. "So when you start talking about it afterwards, it's really, really interesting. I'm always intrigued how people respond to a piece of art. And talking about a character allows me to exorcise it and really let it go. It's quite nice when you kind of get to say goodbye to a character."
Looking at the hectic schedule she was handed before leaving her London flat for Toronto, she did admit to one tiny concern.
"I'm not sure I'll have time for a wee," she said. "I may have to schedule pee breaks if they haven't been scheduled in."
– The Hollywood Reporter