Frances Shand Kydd, 68, who had an often turbulent relationship with her late daughter, Princess Diana, died June 3 at her home in Scotland.
Mrs. Shand Kydd, whose health had been failing in recent months, had been taken a number of times from her home on Seil Island, where she led a reclusive life, to a hospital in nearby Oban. The cause of death was not disclosed.
Queen Elizabeth II sent a private message of condolence to Mrs. Shand Kydd's son, Earl Spencer, Buckingham Palace announced. Prince Charles said his former mother-in-law "will be sorely missed." Prince William said he and his brother, Harry, "are very upset by the death of our grandmother and we will miss her a lot."
Roman Catholic Bishop Ian Murray of Argyll and the Isles said that Mrs. Shand Kydd "once said that her father had taught her to treat everyone the same, whether they came from 'castle, cottage or caravan.' That was a lesson she lived out very well, and many people, from all walks of life, will be saddened by her passing."
She was born Frances Ruth Burke Roche, daughter of the fourth Baron Fermoy. Her mother, Lady Ruth Fermoy, was a confidante and lady-in-waiting to the late Queen Mother, and later was said to have had a hand in promoting Diana's 1981 marriage to Charles.
Mrs. Shand Kydd married Edward John Spencer in 1954 at Westminster Abbey. They had three daughters -- Diana was the youngest -- and a son.
The marriage foundered in 1967 when she fell in love with Peter Shand Kydd, a wallpaper heir who was married. She divorced Spencer to marry Shand Kydd in 1969, when the future princess was 6.
Diana stayed with her father after the split and decades later told Andrew Morton, author of the 1992 book "Diana, Her True Story," that her childhood was unhappy and unstable, particularly during the divorce.
Mrs. Shand Kydd acknowledged she sometimes had a turbulent relationship with her famous daughter. Testifying two years ago at the theft trial of Diana's former butler, Paul Burrell, she said she had not spoken to Diana in the last four months of her daughter's life and that the princess had returned her letters unopened.
Diana and her companion, Dodi Fayed, were killed Aug. 31, 1997, in a car accident in a Paris tunnel.
Mrs. Shand Kydd said she was frustrated by her inability to shield her daughter from intrusions on Diana's privacy and also blamed the media for the failure of her second marriage in 1988.
In addition to her son, Mrs. Shand Kydd is survived by daughters Lady Jane Fellowes and Lady Sarah McQuorquodale. Her stepson, Adam Shand Kydd, 49, died in April from an overdose of sleeping pills in Cambodia.