Taylor Swift’s “Bad Blood” music video debuted during the Billboard Music Awards on Sunday night, but Katy Perry, the woman the song is reportedly about, wasn’t too concerned. The “Dark Horse” singer and Swift, 25, allegedly aren’t on friendly terms after a feud that may have involved stealing one another’s backup dancers and mutual romances with crooner John Mayer.

“She saw it. She thought the video was a little desperate and that she tried too hard, but she isn’t going to worry about Taylor too much because she has her own career to worry about,” a source told Hollywood Insider on Monday. “Bad Blood” starred Swift and a number of other female celebrities, including Gigi Hadid, Cindy Crawford, Jessica Alba, Karlie Kloss, Selena Gomez and Lena Dunham. Gomez starred as “Arsyn,” who plays the partner who betrays Swift. Gomez even wears a wig similar to Katy Perry’s -- a short, black bob.

“For years, I was never sure if we were friends or not,” Swift said in an interview with Rolling Stone on Sept. 8, 2014, though she didn’t name Perry. “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?’”

Swift denied that the feud between her and the unnamed pop star was over a guy. “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 ... I don’t think there would be any personal problem if she weren’t competitive,” she said.

The source confirmed to Hollywood Insider that Perry knew the song was about her. “She felt slighted with the song but the video didn’t really bother her.”

Why do the two musical powerhouses hate one another? There may be a few reasons. Swift dated “Your Body is a Wonderland” singer John Mayer in 2010. Her song, “Dear John” was written about him. Perry dated Mayer two years later. A number of backup dancers also abandoned Swift’s tour to return to Perry’s, according to TMZ, though they reportedly worked for Perry first.