Sarah Ferguson and Camilla Parker Bowles reportedly had a row.

The Queen invited the Duchess of York to join the royals in Balmoral during the summer break. It has been a tradition for the family to visit Queen Elizabeth II in Scotland at this time of the year and enjoy the summer there. However, things allegedly went awry between Ferguson and Camilla.

According to Isabella Sullivan, a journalist for Express, Camilla and Ferguson fought over Princess Diana. There's reportedly a long-standing tension between the two women who have different roles in the late Princess of Wales' life.

Ferguson was very close to Princess Diana. In fact, many believed that the two were best friends. On the other hand, Camilla and Princess Diana's relationship isn't that good due to the former's affair with Prince Charles.

Prince Andrew's ex reportedly couldn't hold it anymore and confronted Camilla after dinner drinks. Ferguson reportedly holds Camilla guilty due to the pain she caused to Princess Diana.

Ferguson admitted that she and Princess Diana were not on speaking terms before the latter died. According to Sullivan, in another report, Princess Diana stopped talking to Ferguson after the Duchess of York confessed in her 1996 book "My Story" that she got a veruca after borrowing Princess Diana's shoes.

Prince William and Prince Harry's mom was reportedly upset that Ferguson even mentioned her when she already promised not to talk about her. Ferguson continued to talk about her former friend in her other books.

"Diana was one of the quickest wits I knew; nobody made me laugh like she did," Ferguson wrote in her 2011 book "Finding Sarah". "We took vacations together with our children. Sadly, at the end [of the Princess's life] we hadn't spoken for a year, although I never knew the reason, except that once Diana got something in her head it stuck there for a while."

Meanwhile, journalist Sue Arnold claimed that Princess Diana didn't mind being compared to Ferguson. In fact, the People's Princess reportedly befriended Ferguson because "she's no real competition."

"Fergie, as she's known to her friends, is a jolly nice girl, supremely suited to the role of second-string daughter-in-law, horsey, bouncy, with an unthreatening I.Q," Arnold said. "Diana chose well, for though Sarah is pretty, she's no real competition. In looks and attitude, she is the perfect foil to the charismatic Diana."