If Taylor Swift wants to end the bad blood between she and Katy Perry, she's going to have to do this, first. According to E!, when Perry was asked by a fan on Twitter if she would ever collaborate with Swift, her answer was simple: "If she says sorry, sure!" That apology from Swift would be for her song "Bad Blood," which reportedly is about Perry "stealing" Swift's backup dancers. While Swift has never officially confirmed the 1989 track is about Perry — she told Rolling Stone in 2014 it was a about a "pop star" who stole her dancer — the California girl definitely thought the song was about her. Perry tweeted shortly after the Rolling Stone profile, "Beware the Regina George in sheep's clothing..." But Perry may be waiting a while for an apology from Swift, who is known to write songs about exes and others she's not too fond of with reckless abandon. Though she'll never confirm or deny who these songs are about, telling GQ last year, "The fact that I’ve never confirmed who those songs are about makes me feel like there is still one card I’m holding." She's allegedly written songs about ex-boyfriends, such as Harry Styles, Jake Gyllenhaal, and John Mayer, who told Rolling Stone he was "humiliated" by Swift's "Dear John," which has her singing "Don't you think I was too young to be messed with?"
Swift has written about Kanye West ("Innocent") and actress Camilla Belle ("Better Than Revenge"), as well. And though she admitted to The Guardian that the latter song was a bit immature, she never publicly apologized to either one. However, she did say "Back To December" — believed to be about her ex Taylor Lautner — was an apology song. Her first, in fact. "I've never felt the need to apologize in a song before," Swift told MTV in 2010. "But in the last two years, I've experienced a lot, [including] a lot of different kinds of learning lessons. And sometimes, you learn a lesson too late and at that point you need to apologize because you were careless." But even that wasn't an actual apology to Lautner, who recently (kind of) confirmed the song was about him, it was just an explanation of the song. So basically, don't hold your breath waiting for that Perry-Swift duet, because it could be a long time coming. A really, really long time.