The Grammy Award winner, 32, reunited with All Too Well star Sadie Sink on the red carpet Friday, ahead of a conversation moderated by TIFF CEO Cameron Bailey about the short film, which Swift directed, inspired by her song of the same name from Red (Taylor's Version).
During the talk, she opened up about the decade-long journey to creating a visual element for the song, which was first released in 2012 as part of her fourth studio album, Red.
"There would be no world in which I could've made a visual element to that song at that point in time," Swift said. "I needed 10 years of sort of retrospect in order to know what I would even make to tell a version of that story visually. And I'm so grateful that I was able to do that with some crazy stroke of all these different twists of fate. I can't believe it."
In the short, Sink, 20, plays a surrogate for Swift, named Her, tracking her dramatic love story with Him (played by Dylan O'Brien) to its heartbreaking conclusion.
All Too Well: The Short Film previously earned Swift three MTV Video Music Awards last month, including best longform video, best direction and video of the year. All Too Well is also eligible for an Academy Award nomination in the best live action short category at next year's awards show.
Sink, who is also promoting her role in The Whale at TIFF, previously admitted to being a Swiftie in real life back in May as she told Netflix's Tudum that Swift's "The 1" was at the top of her Spotify Wrapped last year.
She also revealed that Swift's "August" would be the song to rescue her from Stranger Things season 4 villain Vecna, after her character Max escaped his clutches. "That song honestly can revive me from anything," Sink said.
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The actress also opened up about how her Stranger Things and All Too Well roles compare. "It's tricky because they're such different situations," she explained.
"I put a little bit of myself into both. You're always going to put a little bit of yourself into whatever character you're playing," Sink added. "At the heart of it, they're both definitely independent."