Last Dance? J.Lo 'Frustrated,' Crabby With Dancer Beau

By Kat Giantis

Are Casper Smart's days of living in the lap of luxury as Jennifer Lopez's arm candy numbered?

Just one day after her attorneys threatened legal action over dueling tabloid reports accusing the tatted-up 25-year-old dancer of visiting either an exotic massage parlor or a gay peepshow, celebrity-friendly People magazine hints at a growing rift in their 10-month romance.

"She's getting frustrated with him," shares a source, adding that J.Lo, 43, is increasingly "short-tempered" in his presence.

Lopez rebounded with Casper just a couple months after she called it quits with husband No. 3 Marc Anthony, and they were soon joined at the hip. The backup hoofer tagged along on family vacations with her 4-year-old twins and posed with her blindfolded, leading skeptics (ahem) to conclude that he was on the fast track to become her fourth ex-husband.

"He's moved into her life -- and a little too easily, too," the insider huffs to the mag. "I think her family is watching him closely."

Jennifer's apparent "cold front" with Casper comes a little more than a week after he was photographed outside a New York building that houses the adult-themed establishments featured in the tabloids.

Read on for much more, including why Smart could end up sticking around for a while ...