According to the insider, Jen’s pals are “warning her to proceed with caution because of the singer’s rep as an unrepentant Romeo.”
The source went on to allege that John makes his ladies fell like they are the only one in his life, before he dumps them cold.
Jen dated John for about a year before he dumped her.
Despite their breakup, it was recently revealed the former couple were good friends.
"Jen and John have a nice friendship. John has a deep admiration and respect for Jen,” another source told US Weekly.
“Whenever they talk or are out together it's always friendly and nice. There is definitely no weirdness between them," the insider claimed to the American publication.
Jen has also spoken about John fondly in the past admitting: "We care about each other. It’s funny when you hit a place in a relationship and you both realise, we maybe need to do something else, but you still really, really love each other. It’s painful."
She told People: "There was no malicious intent… I deeply, deeply care about him; we talk, we adore one another. And that’s where it is.”