Is John "Just Not That Into" Jen?

While Jennifer Aniston and new boy-toy John Mayer play kissy-face around Miami, the former Mrs. Brad Pitt might be best advised to take the title of her upcoming film, He's Just Not That Into You, to heart.

The 39-year-old former Friends star showed that she wanted to be way more than that with her musician beau last weekend, casting caution to the wind with some serious poolside PDA at Miami’s Mandarin Oriental Hotel. But while she stared lovingly at him, a bored-looking John gazed into the distance.

This one-sided clinginess has raised concerns among Jen’s pals, who fear the 30-year-old singer/songwriter is, well, just not that into her.

“John says that Jen and he have a physical connection as deep as their spiritual one,” a pal of the Grammy winner tells OK!. “But he also said he’s categorizing this as a summer fling for now.”

The pal points out that John, last linked to actress Minka Kelly, has “never been faithful to anyone.”

But another friend tells OK! that’s not true.

“He’s a serial dater, but he’s never cheated on a girl!” the source tells OK!. “He’s making the effort to fly to Miami to be with Jen. That says something.”

For his part, John seemed to return the affection at the Marley & Me afterparty, where the two were described as "inseparable."

"They were holding hands and being extremely cuddly, kissing and walking with their arms around each other," an eyewitness tells OK!. "They spent the majority of their time sitting on a couch in the courtyard, away from everyone else, foreheads touching, talking to one another."