Katy Perry and Rihanna were always close friends, but that friendship has come to a nasty halt, all over one guy…who you ask? Chris Brown, of course.

Reports from Music-News indicate Katy is “incredibly angry” over Rihanna’s decision to renew her relationship with Chris Brown after what happened last time.

Katy feels Rihanna shouldn’t have to be in an abusive relationship again, and although there are no outward signs that Chris has fallen into his old ways with Rihanna, Katy believes people cannot change.

“Katy was always the one person who could really stand up to Rihanna,” a source close to the star told Grazia magazine (quoted by Music-News).

Along with voicing her concerns over Chris, Katy worries Rihanna has fallen down a dangerous and destructive path with her lifestyle choices and health, but she is voicing her concerns to deaf ears.

“She has stuck her neck out for Rihanna, and so it really hurt when Rihanna ignored her advice,” added the source. “Katy told Rihanna that she couldn’t stick around and watch someone she loves make such a big mistake, and that she had to walk away.”

Walking away meant breaking all ties, and now it’s been months since the two have spoken.

-Ashley Quadros, CBS Local