The romance between Jennifer Aniston and John Mayer may be kaput, but the rumor mill is still cranking at full speed. The latest theory: The actress, 39, who just a week ago was being touted as a future bride and mother, was the dumper, not the dumpee.

John appears to reach for Jen's hand as they brave a paparazzi barrage at the wrap party for "Marley & Me" in Miami.

While a snitch informed the London Daily Mirror that the crooner, 30, was the one who pulled the plug on their four-month interlude because "he felt he just wasn't ready for the level of commitment that Jennifer deserved," the Chicago Sun-Times believes that the decision to part ways was all hers.

"[It was] Jen who decided to move on," says a source described as being "super-close to both Aniston and her best pals Courteney Cox and David Arquette." "She is very fond of John and has thought he might be the one. She finds him funny, sexy and very talented. Plus, he understands all the aspects of living in a fishbowl."

The problem, according to the snitch, is that "in the final analysis, she just got tired of his roving eye."

And here's where a big ol' grain of salt might come in handy, because the paper claims Aniston issued a "three strikes and you're out" threat to Mayer after supposedly discovering he'd dallied with two different women.

The paper says "the final straw" was a purported brief encounter "with a groupie."

(This premise, of course, raises one important question: Why not one strike and you're out?)

"Above everything else, Jennifer is looking for stability and loyalty in a relationship," opines another Aniston mole, who then unwisely plays up the public's perception of the former Mrs. Brad Pitt as an unlucky-in-love pity partier. "She still is hurting from losing Brad to Angelina [Jolie] -- even after all this time."

And what of the tabloid rumor that Jen is seeing a model identified as one Matt Felker, who appeared in Britney Spears' "Toxic" video and fancies himself, at least if an online photo gallery is any indication, something of a Brad-alike?

Spies insist to Perez Hilton that there's no romance going on, adding that Aniston doesn't even know the beefcake in question.

Mayer, for his part, was uncharacteristically press-shy as he arrived at his apartment in New York on Thursday after jetting in from Los Angeles.

The singer, who recently enjoyed a getaway to Cabo San Lucas, Mexico, that included a hot tub soak with a couple of bikini-clad lovelies (said to be pals), kept his face buried within a hoodie as he made a beeline inside, ignoring paparazzi who tactlessly lobbed Aniston-related questions his way.