Chris Brown is having his 'Birthday Cake' (cake cake cake cake cake cake cake...) and eating it too. Despite still being in a relationship with model Karrueche Tran, the 'Don't Wake Me Up' singer engaged in a pretty public liplock with former flame and rumored current sidepiece, Rihanna, at the 2012 MTV Video Music Awards -- and Tran ain't too happy about that.

A source told Us Weekly that Tran is "totally pissed off" that Breezy kissed RiRi following her Video of the Year victory. "She felt the kiss was a public slap in the face." Uh, no kidding. Especially considering Brown only decided to attend the VMAs at the last minute without even telling Tran. Ouch!

Adding insult to injury is that Rihanna and Karrueche have feuded pretty publicly over Twitter, usually with RiRi, who admitted to Oprah that Brown is the love of her life, as the instigator -- which baffles us, because she's one of the most beautiful and sought after women on the planet. Where does she find the time?! What bugs us most about the warring women is that Rih apparently resorted to a few racist remarks about Tran, who is part Vietnamese.

"[Karrueche] and Rihanna really hate one another and Chris ultimately just does what he wants," the source added. "Seeing him with Rihanna at such a public event made her very angry."

Listen, we love us some Breezy, but is any man worth all this drama and immaturity? Really, the only winner in all this is Brown ... at least until one of these ladies musters up enough self respect to either issue an ultimatum or walk.

Listen to Rihanna Feat. Chris Brown, 'Birthday Cake' Remix