In recent weeks, Justin, 46, has been spotted out with a slew of women, including Selena Gomez, models Erika Cardens and Petra Collins, all 25, as well as actress Aubrey Plaza, 33.
Jennifer Aniston, 49, 'feels like Justin's traded her in for a bunch of newer models,' an insider told Life & Style.
'She considers it the ultimate insult,' the source added.
Life & Style's explosive report adds that it wasn't just the age of Justin's new friends that Jen is finding humiliating, but his constant partying has made her look bad.
'Jen believes they both should have laid low for the first few months and given their relationship a mourning period,' a friends tells the publication.
'Instead, Justin's been acting like a man who was just let out of prison.
'Jen feels betrayed.'
The couple announced the end of their seven year marriage in February.