*The social media world is buzzing over a budding feud playing out on Twitter and Facebook between Chris Brown’s ex-girlfriend Rihanna, whom he dated until he assaulted her in Feb. 2009, and his current girlfriend, Vietnamese model Karrueche Tran.

According to the New York Post, it all started when Tran, 23, quoted Nicki Minaj’s line from “Stupid Ho” on her Facebook page: “I’m Angeline (sic), you’re Jen. C’mon you see where Brad is at.”

Earlier this week, Rihanna appeared to have countered on Twitter with a photo of a bag of rice cakes wearing sunglasses and with gold earrings, with the caption, ”Ima a make u my b**ch,” a line from her latest single, “Birthday Cake,” which features Brown on the remix.

When a follower then tweeted ”@rihanna save me some rice cakes rather hungry,” she hit back with the comment: ”Kinda DRY tho.”

Karrueche is then said to have replied via posts on Facebook, writing: ”Let me clear the air, if you have fenty at the end of ya name or your default Is Rihanna you have a better chance of winning the lottery than ending up on my friends list. (sic)”

However, the model has since denied she has a Facebook page.

This hasn’t stopped Rihanna, who continued to post messages on twitter last night (March 7), writing lyrics from a Lil Kim and Mobb Deep’s track, reading: ”I’m a leader, yall on some followin s**t … coming in dis game on some modeling s**t.”

Although they split in 2009, recently Rihanna and Chris have been seen at a number of the same events, and appeared on remixes of each other’s latest singles.  A source told Us Weekly magazine: ”Rihanna loves to live dangerously, and talking to and hooking up with Chris is all part of that.”