Princess Diana and Sarah Ferguson
Princess Diana was jealous of Sarah Ferguson because she knew how to win the hearts of the royal family. Pictured: Prince Andrew, Ferguson, Lord Linley, Prince Edward, Prince Charles, Princess Diana, Queen Elizabeth II and Queen Mother outside her London Clarence House residence on Aug. 4, 1989. Getty Images/Johnny Eggitt

Princess Diana was jealous of Sarah Ferguson.

The Princess of Wales and Duchess of York were very close at one point. In fact, they were deemed best friends, but their joyous friendship took a turn for the worse. They were not on speaking terms when Princess Diana died in a car crash.

According to royal biographer Katie Nicholl on channel 5’s documentary “Royals at War,” the rivalry between Princess Diana and Ferguson stemmed from within their family.

“There were some rumours of rivalry but I think actually those stem more from within the Royal Family,” the biographer said.

Nicholl pointed out how Prince Charles apparently told Princess Diana why she couldn’t be more like Ferguson.

Also, biographer Andrew Morton cited several reasons why the People’s Princess was “jealous” of Ferguson. Prince William and Prince Harry’s mom couldn’t reportedly believe how Ferguson did all the things she had with the royals.

“She’s carriage-driving with Prince Philip, she’s out shooting with Prince Charles, she’s just a bundle of energy,” Morton explained.

“She was very comfortable in royal circles, and she was very at home marrying into the family.”

Morton pointed out that the royal family is about dogs and horses and country sports. On the other hand, Princess Diana was just an urban girl. Meanwhile, Ferguson was the daughter of Prince Philip’s polo manager. The Duchess of York could relate to the royals when it's about horses and her bubbly personality made the royals warm up to her easily.

Royal biographer Allan Starkie described Princess Diana and Ferguson’s relationship as “highly competitive.” According to him, the two women were fighting an ongoing battle through their charities and both were using the press as their weapon. They looked like actresses on the opening night at the reviews of their charity trips.

He added that both of them compared themselves to each other and whined when the other one got better reviews. When Ferguson promoted an AIDS charity, the People’s Princess reportedly called her and questioned her for trying to “hijack a cause that I’ve done so much for.”

Although they stopped talking to each other, Ferguson said that Princess Diana actually reached out to a common friend the day before the tragic accident looking for Prince Andrew’s ex-wife. Princess Diana told their friend that she wanted to speak with Ferguson. Unfortunately, they never had the chance to talk and rekindle their friendship due to the car crash that killed Prince William and Prince Harry’s mom.