Cat Fight!! Rihanna Nip Slip While Fighting w/ Chris Brown's Ex, Karrueche!! (PHOTOS)

Rumor has it that Rihanna went to Los Angeles night club, Play House, for one reason.... To approach Chris Brown's ex, Karrueche and that's exactly what she did.... allegedly!

Sources say Rihanna walked into Play House, directly to VIP to sit across from Karrueche, who was hosting the party. The source said,

"It was really TACKY for Rihanna to show up, but I guess she wanted to do something."

Then insiders say Rihanna got up and stepped to Karr saying,

"So you wanna TURN UP rice cakes."

What??? Lol Did Rihanna really say that?

Well, according to this source...yes!

Then,

"Karrueche just turned away and tried to ignore her. Rihanna's friend [Melissa] was just there laughing."

This is not confirmed, but what we do know for sure is that RiRi did indeed crash Karr's party and she did also show off her "nip slip" with this see-through dress!