While the reason for the souring of friendship remains unclear, media outlets have dubbed Rose the Duchess' "rural rival".
The two women, both part of an elite set of Norfolk aristocrats, are both mothers-of-three and previously enjoyed playdates with their children and dinner parties with their respective spouses.
Rose, 33, is a former Storm Agency model and the wife of 58-year-old David Rocksavage, Marquess of Cholmondeley.
The affluent couple live at Houghton Hall, just three and a half miles from Kate and William's country residence Anmer Hall on Queen Elizabeth's Sandringham estate.
Rose's family have far reaching history with the Windsor dynasty.
Her grandmother, Lady Elizabeth Lambert, was a childhood playmate of the reigning Monarch and even stood as one of her bridesmaids at her wedding to Prince Phillip in 1947.
At their Devon home yesterday, Rose's parents Tim and Emma flatly declared they had "no comment" about their daughter's alleged dispute with the Cambridges.
Daily Mail reached out to the Marquess and Marchioness of Cholmondeley but a member of staff replied: "They are not available today."
Asked if the couple knew about the allegations, the employee answered: "We are fully aware."
One source told The Sun: "It is well known that Kate and Rose have had a terrible falling out. They used to be close but that is not the case anymore."
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