Her ex is in a new relationship, and her sister's a smitten kitten. But how's Jessica Simpson doing these days? Not too well! She's "really jealous" that John Mayer's hooking up with Cameron Diaz, a source tells Us Weekly. "She thinks about him all the time," the insider says. "She is so not over him." Maybe that's why she didn't take well to the news of John's new paramour. "She had her mouth open a mile wide when she found out," the source spills. "She just freaked."

On the other hand, John doesn't seem too hung up on Jess. A source close to him says that he and Cam are "happy." Ouch.