The rumours began after People Magazine reported that Kate flew to Paris to see Matt play, before enjoying a cosy walk with the rocker the next day.
“They seemed very much a couple,” the source told the magazine. “Just walking together, enjoying the sunshine.”
This wouldn’t be the first time Kate has dated a musician.
She was with The Black Crowes’ frontman Chris Robinson from 2001-2006. The couple got married and had a son together.