After Taylor Swift debuted her music video for “Bad Blood” rumors started circulating that the song was about her used-to-be friend Katy Perry. The two pop stars used to be good friends, they posed together at award shows, tweeted to each other, and Swift even invited Perry as a guest star in one of her concerts. So what happened to the friends turned enemies?

TAYLOR SWIFT AND KATY PERRY’S FEUD

Swift explained her inspiration for “Bad Blood,” telling them that an unnamed female artist had crossed the line with her way too many times in an interview with Rolling Stone. “For years, I was never sure if we were friends or not,” she said. “She would come up to me at awards shows and say something and walk away, and I would think, ‘Are we friends, or did she just give me the harshest insult of my life?'”

Then last year, according to Swift, the mystery star crossed a line. “She did something so horrible,” Swift said. “I was like, ‘Oh, we’re just straight-up enemies.’ And it wasn’t even about a guy! It had to do with business. She basically tried to sabotage an entire arena tour. She tried to hire a bunch of people out from under me. And I’m surprisingly non-confrontational – you would not believe how much I hate conflict. So now I have to avoid her. It’s awkward, and I don’t like it.”

Later in the interview, the 25-year-old expresses that she did not want “Bad Blood” to be all about calling out the mysterious celebrity who crossed the line with her. “My intent was not to create some gossip-fest,” she said. “I wanted people to apply it to a situation where they felt betrayed in their own lives.”

Soon after the article was published, a lot of rumors started spreading that the female artist Swift was talking about might be Perry. To add even more fuel to the fire, Perry tweeted, “Watch out for the Regina George in sheep’s clothing.” The Mean Girls reference seemed to be obviously about Swift, which caused for more rumors.

Gossip sites pointed out that the “business” situation that happened between Swift and the female artist could be referring to when three of Perry’s backup dancers for the California Dreams 2011 tour were hired for Swift’s Red tour after Perry’s had ended. While the backup dancers were touring with Swift, Perry’s people allegedly reached out to the dancers asking if they’d want to return for the star’s upcoming Prism tour, which would require them to leave Swift’s early. The dancers ended up leaving Swift’s tour early, and Swift unfollowed them on Twitter. This week, Perry, 30, was caught liking an Instagram account titled “sl—-taylorswfit.” Though the Instagram account has that name, the photos are just of a girl who resembles Swift, and there’s nothing provocative about the account. Perry’s subtle social media dig was right after Swift’s performance of “Bad Blood” at her concert in Foxborough, Mass., on Sunday. Apparently, while singing the song, one of Swift’s backup dancers held up a stuffed shark puppet – referencing Perry’s famous 2015 Super Bowl halftime performance.

Watch the performance and the appearance of “Left Shark” below:

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