Katy Perry, John Mayer Dating: Jennifer Aniston Thinks Perry Should Dump Him

Things are heating up between Katy Perry and John Mayer, but at least one A-list celebrity thinks Perry should run in the opposite direction.

Sources say Jennifer Aniston, who dated Mayer for about a year and is now engaged to marry actor and writer Justin Theroux, has been telling friends that Perry should open her eyes to Mayer's womanizing ways and get out while she still can.

An insider close to Aniston said Perry should learn from what happened between the former "Friends" star and Mayer, according to a new report from Perez Hilton.

"Katy should really watch out. Take it from Jen. She's been there and done that," the source said. "And it took her years to recover. Jennifer gave John more than a year to prove himself as marriage material. Katy needs to be warned about John's hypnotic ways before its too late."

But it seems Perry isn't listening to any detractors of her relationship. Hollywood Life reports that pals of Perry say she is head over heels for Mayer.

"It's the real deal. They just understand each other and Katy is happy to be with someone who isn't uptight and controlling. John is all about having fun, and so is Katy," a source said.

And not only is the relationship "the real deal," but Perry is already thinking about taking the next step.

"Even though Katy is acting aloof, she's pretty much crazy about him. John could be the one for Katy, she's never felt this way," the insider said.

The source added that it's not only Perry who is infatuated with the relationship. Mayer loves Perry's independent streak, which he hasn't found in many other women.

"John likes being around Katy because she isn't needy," the in