The bad blood is believed to boil over at Princess Eugenie's October 12 wedding to Jack Brooksbank.
Eugenie was determined to make sure her lavish wedding bash was bigger and better than Meghan's May nuptials.
The royal invited over 850 guest, compared to Meghan's 600.
According to GLOBE's sensational report, Camilla is using the young royals' feud as a way to weaken the growing bond between Meghan and Kate - who she sees as rivals for the public's affection and influence in royal circles.
She has been pitting both sides against one another, insiders claim.
"When Camilla gets together with Beatrice and Eugenie she joins in the talk about how trashy and common Meghan and Kate's lineage is," a palace insider explosively tells.
"When she's around Kate and Meghan, Camilla will talk about Andrew's daughters being spoilt."
"The feud definitely threatens to tear the royal family to shreds as relatives begin taking sides."
Although the royal family are yet to respond to GLOBE's report, earlier this week it was revealed that "bridezilla" Eugenie had attacked Kate Middleton and given her strict rules.
The stressed-out bride is not only said to have attacked poor Kate by insisting she was forbidden from arriving through the main entrance, but Eugenie’s diva demands, fights with the wedding planners and blow out budget mean the event is swiftly turning into a disaster.
An insider told New Idea, jealous Eugenie insisted Kate – who is looking as glamorous as ever following her return from maternity leave – entered through a side entrance, out of the main stream of cameras, in order to avoid the duchess taking away her limelight.
Following news that over 23,000 people had signed a petition demanding the British government not commit any public money to the Oct.12 nuptials, insiders say the princess had a “bridezilla meltdown” and the “wedding rehearsal from hell”.
Royal sources are claiming Eugenie attacked her wedding planner, Peregrine Armstrong-Jones – who is from prestigious event planning company Bentley’s Entertainment, and known for having organised previous royal weddings – for not doing his job properly.
“Eugenie went ballistic at the final meeting with her planners – demanding they make a string of last-minute changes and throwing a hissy fit over various details which she insisted she hadn’t approved,” a source spills.