Princess Diana Suspected Pal Sarah Ferguson Was 'Selling Stories' Before Her Tragic 1997 Death, Royal Expert Claims

Sarah Ferguson and the late Princess Diana were once great friends and even sisters-in-law for a while — but a betrayal tore them apart.

According to a royal expert, the Princess of Wales became angry with the ex-Duchess of York, 66, when she published her 1996 memoir My Story.

Royal expert Richard Fitzwilliams told Fox News on Tuesday, June 9, how Diana — who died at the age of 36 in a 1997 car crash — assumed Ferguson was "selling stories" to the press. She was reportedly also "angered by mentions of her sons [Prince Harry and Prince William] in her book."

Despite Ferguson frequently apologizing for penning the memoir, Diana ignored her. "If [Diana] had wanted to renew their friendship, she would have," Fitzwilliams added of how their relationship went south.

Royal author Andrew Lownie also touched upon Diana and the former Weight Watchers spokeswoman's friendship in his recent book Entitled.

The pair often jokingly referred to themselves as the "Terrible Twins" and the "Wicked Wives of Windsor."

Ferguson was married to ex-Prince Andrew from 1986 until 1996, with Diana and King Charles tying the knot in 1981. They also divorced in 1996.

"The two women — once close — had not spoken for months after Sarah had written about her sister-in-law against Diana's wishes in her memoir and made a joke about catching a verruca (wart) from one of Diana's shoes," Lownie penned. "The two were fourth cousins and had known each other since they were teenagers — their mothers had been at school together — and shared the experience of their mothers being denied custody of their children."

Royal expert Helena Chard further discussed the women's fractured relationship with Fox News, claiming Lady Di had to "cut ties" because Ferguson's memoir "brought their private tensions into public view."

"It was the final straw, and alarm bells rang as Diana read conversations referring to her sons," Chard noted, adding the People's Princess felt betrayed because Ferguson was "leaking personal information and trading on their conversations."

"Diana's privacy was her safety," Chard said. "She was fastidious about controlling her narrative. She used private information strategically."

The author alleged Diana and Ferguson never squashed their beef before Diana's sudden death.