Swift first connected with "Girls" creator and actor Lena Dunham via Twitter in 2013, per Insider. The two shared a mutual love for one another, and were first pictured together at the Grammys that same year. Dunham, who previously dated producer Jack Antonoff (whom Swift frequently collaborates with), served as the inspiration for Swift's 2015 song "You Are In Love" from her "1989" album.
In an interview with Elle, the singer referenced the lyric "You're my best friend," explaining, "Yeah. I've never had that, so I wrote that song about things that Lena [Dunham] has told me about her and Jack [Antonoff]. That's just basically stuff she's told me. And I think that that kind of relationship—God, it sounds like it would just be so beautiful—would also be hard. It would also be mundane at times."
Like many of Swift's other friends, Dunham also made an appearance in the "Bad Blood" music video. In Dunham's September 2021 wedding to Luis Felber, Swift had a special role as a bridesmaid, per W Magazine.