Marc's Wife: Cool It With J.Lo!

Since her split from Casper Smart, Jennifer Lopez, 47, has been spending more time with her ex-hubby and baby daddy Marc Anthony — and their chummy relationship has his 28-year-old wife, Shannon De Lima, on edge.

"Shannon understands that Jen will always be in Marc's life because of their kids, but she felt more secure with their bond when Jen was dating someone," says a source.

Now that the exes are collaborating on an album, and even duetted at a recent J.Lo performance, Shannon's "worst fears are coming true," says the source.

"She worries she can't compete." Who could?