Rihanna and JR Smith 'Flirt, Party?' PHOTOS: After Chris Brown Break Up, Karrueche Tran Reunion, Onstage Diss, RiRi Moves on, Dating NBA Ex-Flame?

RIHANNA AND CHRIS BROWN BREAK UP! Shocking.

Rumors have it that after rekindling a short-lived romance, RiRi and Breezy have split up once again. Apparently, Brown's even started to hang out with his ex-girlfriend, Karrueche Tran. But no worries - Rihanna's allegedly having a good time partying and flirting with a sexy ex-flame of her own... NBA star JR Smith!

Both Rihanna and Brown have been spotted partying a lot... sans their significant other. That's put a rather detrimental strain on their relationship and as-of-now they're no longer together:

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Apparently, Breezy recently skipped-out on RiRi's "Diamonds" concert in Brooklyn and spent the evening partying in Harlem instead. And that was the final straw. During the live performance, Rihanna announced to the crowd:

"Anybody who thinks love is the most complicated sh#t ever? This is for us complicated ones. What the f#ck now..."

She then went on to sing "What Now."

And while Brown spent his birthday celebrating with Tran over the weekend, Rihanna was previously spotted with another man... New York Knicks baller JR Smith. Both stars hit up NYC's Greenhouse nightclub on April 24, and several eyewitnesses claim the sexy chemistry was definitely obvious. One insider tells Hollywood Life:

"Rihanna arrived with her girlfriends at Greenhouse around 1 am. Rihanna had security escort her down to the DJ booth table where Iman Shumpert and ex-boyfriend and bad boy JR Smith were sitting. The Knicks players had just beat the Celtics and they were out celebrating. It was really clear to everyone that there is some awkward tension still between RiRi and JR, but she was dancing really sexy in front of him, showing off almost. JR later went up to VIP and sat with Rihanna for a bit after she got on the mic to shout out to the NY Knicks, 'the greatest team in the world,' big win."

The source continues:

"Rihanna and her girls danced the night away in VIP with spotlights on them. She knew all eyes were on her. She gave her phone to her assistant for the night and asked to not have it back till 'after they were done partying'. Rihanna left with her girls (no guys) around 4 am, out the back door and went back to their hotel, Gansevoort Park. Rihanna stopped by JR's table on her way out to give him a kiss and a hug."

The two were "flirting all night," according to a MediaTakeOut insider. Check out a pic of the two hanging in VIP here.

RiRi and Smith apparently had a little romantic "fling" going last April. Rihanna then went on to work things out with Brown.

Still, another source insists the RiRi/Breezy break-up won't last long (like always) - "They ain't never going to be done... They're just coolin it right now. There's always going to be love there. That will never change. But sometimes its better to take a break and get back to the basics."

So are things heating back up between the "We Found Love" songstress and the popular NBA point guard, or are they just good friends and party buddies?