Nicki Minaj vs. Jennifer Lopez 'Beef' - 'Booty' Beauty Disses 'Anaconda' Twerking at Fashion Rocks 2014, Jealous Of 'Budding' Casper Smart Relationship? [WATCH]

YMCMB sweetheart Nicki Minaj stunned the crowd at the 2014 Fashion Rocks charity fundraiser with a sexy rendition of "Anaconda" - check it out (don't mind the rather entertaining fan commentary featured in the clip):

The audience went totally crazy when Minaj flaunted her impressive twerking skills. Well, almost everyone...

However ,fellow songstress Jennifer Lopez didn't look too happy throughout the rapper's entire performance!

The popular gossip webloid HollywoodLife.com captured this screenshot of J-Lo during the show, and she kept a sour face on basically the whole time...

No emotion, no dancing... just a straight-lipped look of "disapproval."

For those fans who didn't know, the "Booty" beauty recently broke things off with younger (ex) boyfriend, Casper Smart - the same choreographer who worked closely with Minaj on the epic "Anaconda" music video:

Rumors suggest that the two got "really close" while working together... just professionally, of course. Smart also helped prepare the 31-year-old twerker for her racy performance at the 2014 VMAs back in August.

So, maybe Lopez is jealous? Or was she just "bored" during the wild booty-shaking performance? Just moments before, Lopez got onstage and shook her own goods. Another thought - perhaps there's a little competition "beef" brewing between the two hip-hop divas...

What do Mstars fans think?