The video for 95.8 Capital FM played right before Tay took the stage at Hyde park and featured a whole bunch of artists like Ed Sheeran, Sam Smith, One Direction and, of course, Katy. The first time Katy appeared on the screen, there was a low booing, but it was clear that the crowd was showing their disapproval. The second time Katy appeared on the vid, the crowd erupted in a very loud boo, which was replaced by cheering when Taylor appeared on the screen right after.
It's not surprising that Tay's fans would boo Katy because when celebs are feuding, their loyal fans can sometimes get more upset about it than the stars themselves.
Neither Katy or Taylor has directly confirmed the feud, but there have been enough not-so-subtle jabs back and forth for people to make assumptions. In fact, Taylor's song "Bad Blood" is reportedly about her feud with Katy.
We're still holding out hope that these two settle their differences and come together to make the greatest pop superstar collab that ever was.
In the meantime, Tay did squash one feud rumor during the same concert - the one about her and Kendall Jenner. During her performance of "Style," Tay brought a bunch of her gal pals up on stage and Kendall was one of her peeps.