'It Ends With Us' screenwriter on landing a Taylor Swift song for the movie's soundtrack: 'It's as if she wrote it for this'

• Blake Lively's new movie, "It Ends With Us," features a Taylor Swift needle drop during a key scene.
• Screenwriter Christy Hall spoke to BI about her reaction to getting the cosign from Swift.

The emotional climax of Blake Lively's new movie, "It Ends With Us," features a Taylor Swift song so fitting that "it's as if she wrote it for the movie," according to screenwriter Christy Hall.

Hall, who was also a producer on the film, spoke to Business Insider about Swift's involvement in the project — which earned her a special shoutout in the film's closing credits.

"It Ends With Us" is based on Colleen Hoover's best-selling novel of the same name.

It follows a florist named Lily Bloom (Lively) who falls for a neurosurgeon named Ryle Kincaid (Justin Baldoni, who also directed the movie).

When Bloom runs into her first love, Atlas Corrigan (Brandon Sklenar), painful memories from her past start to surface, and she realizes that she's not living the dream but a nightmare.

Swift's gut-wrenching "My Tears Ricochet" from her 2020 lockdown album, "Folklore," comes in at a pivotal moment for the character.

Swift's endorsement is a big deal these days, and Hall said it was a "huge deal" to get the Grammy-winning star to cosign the film.

"I'll never forget that day when I learned that it was happening. My jaw was on the floor," Hall said. "It took hundreds of people collectively to make this movie, and everyone played their part, and this was the little cherry on top."

Hall said that while they were already proud of the film, having Swift add "one of her most cherished songs" could not have been "more perfect."

"It's as if she wrote it for this movie, though she did not. It was just such a huge win for the film," Hall added. "It's such a beautiful reflection of her dear friendship with Blake."

Swift is godmother to Lively's four children, who she shares with her husband, Ryan Reynolds.

Swift's involvement in the movie doesn't end there, however. In the end credits for "It Ends With Us," Lively gives the "Fornight" singer a special shoutout.

It's not known exactly what contribution Swift made to the movie beyond lending the song — Hall didn't divulge — but Lively also included other close friends and family in her list of thank-yous shown at the end of the movie.

They included her children, her brother Austin Swift, Bradley Cooper, Britney Spears (whose song "Everytime" is covered by Ethel Cain in the film), Aaron Dessner, and Shawn Levy (who directed "Deadpool & Wolverine."

"It Ends With Us" is in theaters on August 9.