Rihanna & Future Hook-Up Prompts Broken Engagement? Ciara Dumps Fiance Amid RiRi Beef, Cheating Buzz, & 'The Monster' Tour 'Crush' Eminem

It's no secret that Ciara broke things off with ex-fiance Future because he was allegedly cheating. But with how many girls, exactly?

Apparently, Future's flirtatious relationship with fellow songstress Rihanna is what ultimately led CiCi to end the engagement for good.

Oh, there's also personal assistant Tyrina Lee, a sexy Instagram groupie @_ImGorJess, baby mama Brittni Mealy...

The list continues growing.

Anyway, the popular Atlanta emcee and the "Pour It Up" beauty have been working on a new music collaboration all summer. Several fans were led to believe they were bonding in AND out of the studio...

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And now, a supposed snitch reveals to the infamous gossip webloid MediaTakeOut.com that Ciara strongly dislikes 26-year-old RiRi - she could deal with some side chicks, but not this specific one. Future started acting shady, and CiCi got suspicious:

"Future promised that he would just make music and then come back home to be with Ciara and their baby," the alleged source explains. "But he was out in the club with that HEAUX [Rihanna]." 

The insider continues:

"Future is a rapper, so he's going to be messing around. It's one thing if he's with some stripper on the road, or with one of your baby's mothers. I'm not saying it's right, but things happen. But to be [allegedly] f*ckin the nasty b*tch that your fiance HATES... while Ciara's at home taking care of your baby less than a mile away. That's some sh*t you just can't forgive." 

Fighting words.

Do Mstars readers really think RiRi and Future hooked up, and that's why Ciara was forced to dump her future hubby?

RiRi has yet to say anything on Twitter, although rumors suggest that she might now have a "slight" crush on her "The Monster tour buddy, Eminem...

If these rumors are true, the Barbadian stunner really gets around in the hip-hop industry!