Katy reportedly made a special request to be seated nowhere near the couple at the Grammy Awards in Los Angeles on Sunday (10.02.13).
A source told USMagazine.com: "They aren't tight anymore because Katy doesn't approve of Rihanna dating Chris Brown."
But friends close to Rihanna, 24, insist she has no problem with Katy, 28, but doesn't care what anyone thinks about her relationship because she is happy.
An insider told HollywoodLife.com: "Rihanna doesn't have a problem with anyone and could give a f**k about what anybody thinks about her relationship. She was focused on her and Chris and enjoying her night."
The Part of Me singer was previously said to be barely speaking to Rihanna because she thinks she is "making a huge mistake" by getting back together with Chris.
A source revealed in November: "They're barely talking and ever since the couple reunited, there has been tension between them. Katy has been spending a lot of time with pals Robert Pattinson and Kristen Stewart. Katy fears Rihanna is making a huge mistake and doesn't want to be part of it."
The last time Katy and Rihanna were spotted hanging out together was at the MTV Video Music Awards in September during which Rihanna shared a public peck on the lips with Chris for the first time since their 2009 break-up.
The couple went public with the reconciliation earlier this month and snuggled up to each other in the front row at the Grammys, while Katy sat elsewhere with her boyfriend John Mayer.