Katy Perry and Rihanna are the sort of showbiz BFFs who seem to only hang out at awards shows, but even though they may not have regular slumber parties, that doesn't mean it's okay for either of them to go palling around with the other's exes.
At least that's the message Katy has reportedly delivered to RiRi after learning of plans for a John Mayer/Rihanna collaboration.
Katy, of course, is rumored to be still devastated by her split from Mayer and insiders say she's close to ending her friendship with Rihanna as a result of the planned recording session.
"Katy's been left shocked and hurt after finding out John and Rihanna met up at an LA recording studio two weeks ago before having dinner," an anonymous source told the British tabloid Now.
"Rihanna asked John to sing vocals on a new track," the insider added. "But Katy's flipped out and told her best mate she's gone one step too far this time."
Yes, the "source" on this LA-based drama is clearly British, but the rumor remains plausible nonetheless.
Rihanna's done duets with a number of male singers and if Katy's emotions are as raw as we've heard, it stands to reason she'd be upset to find out her best friend is working alongside her ex.
Katy is dating DJ Diplo these days and seems to have mostly moved on, but RiRi is definitely still violating girl code here.
We'd say Katy should take revenge by collaborating with Rihanna's ex, but Chris Brown is in jail for the foreseeable future and it's hard to duet through a plexiglass window.