It all started with Katy's appearance on Australian talk show Sunrise Tuesday, when she was asked to comment on her and Miley's much-publicized kiss.
"I just walked up to her to give her like a friendly girly kiss, you know, as girls do, and then she like tried to move her head and go deeper and I pulled away," she said. "God knows where that tongue has been. We don't know! That tongue is so infamous!"
Not surprisingly, Cyrus wasn't too pleased with her comments, and responded Wednesday.
Clearly, Miley's alluding to the reports that Katy has split with her on-and-off boyfriend -- and notorious serial dater -- John Mayer.
Video: Watch Miley and Katy Kiss!