'Kate is spitting mad,' a palace insider told GLOBE. 'She told a palace confidant, "I've been betrayed! I bent over backwards to help Meghan find her way as a royal, teaching her the rules, giving her fashion tips and even offering advice on her first pregnancy".'
The insider reveals Kate as saying, '"But instead of using my tips to develop her own polished look, Meghan is simply stealing my style - hair, makeup, fashion, even body language".'
"It's like she's trying to clone me!" a frustrated Kate vented to the palace insider.
GLOBE's insider adds Meghan has sneakily changed from a 'coy rookie to demanding diva' in just two weeks.
'Her new status has gone to her head,' the insider tells the US publication.
'She believes she can pull off the best of Kate's looks - better than Kate - and become Queen Elizabeth's favourite!'
Meghan has studied William's wife from every angle, says the insider.
The escalating tensions have caused Harry and William to be caught in the crossfire.
'The brothers are incredibly close, but this feud is tearing them apart because they're being forced to take sides,' says the source.
'They're desperate for a truce. They're treading a tricky tightrope, trying to keep their bond - and their marriages - in tact.'
The royal family is yet to respond to GLOBE's report.