Katy Perry appears to have hit back at comments from Taylor Swift about her beef with an unnamed pop rival.
In a recent interview with Rolling Stone, I Knew You Were Trouble singer Taylor talked about a song from her upcoming album 1989, Bad Blood, which is about a fall out with another female pop star.
She said of the mystery singer: "For years, I was never sure if we were friends or not. 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?'
"She did something so horrible. 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."
There had been speculation that the enemy was in fact Katy, as both had toured at the same time and both have dated fellow singer John Mayer.
Now, Katy has tweeted: "Watch out for the Regina George in sheep's clothing..."
The comment refers to 2004 film Mean Girls, which starred Lindsay Lohan as a girl at a new high school and Rachel McAdams as teenage queen bee and general bully Regina George.
Katy's followers left comments underneath the tweet that questioned whether she was talking about Taylor, but neither star has confirmed that they have fallen out.