The rift between the pop stars stems from comments that Swift made in a 2014 interview with Rolling Stone magazine, where she noted a shaky relationship with an unnamed artist as the inspiration for her song, "Bad Blood."
"For years, I was never sure if we were friends or not," Swift told the publication. "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?'"
Perry's purported response was a tweet comparing Swift to Mean Girls character Regina George. She later confirmed the rift in a 2015 Billboard interview stating, "If somebody is trying to defame my character, you’re going to hear about it."
Perry has taken swipes at her former friend ever since, including a tweet during Swift's Calvin Harris drama, that now infamous phone call recording with Kanye West, and another possible dig in Elle magazine last year.