LONDON - Frances Shand Kydd, who had an often turbulent relationship with her late daughter, Princess Diana, died Thursday at her home in Scotland. She was 68.

Shand Kydd's health had been failing in recent months and the grandmother of Princes William and Harry had been taken from her home on Seil Island, where she led a reclusive life, to a hospital in nearby Oban a number of times.

A spokesman for her son, Earl Spencer, said Shand Kydd "passed away peacefully this morning, after suffering from a long illness, and this is now a private time for the family to grieve."

Queen Elizabeth II sent a private message of condolence to Earl Spencer, Buckingham Palace said.

The Roman Catholic Bishop of Argyll and the Isles, the Right Rev. Ian Murray, said Shand Kydd was a "deeply spiritual woman."

"She 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," Murray said.

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 was later said to have had a hand in promoting Diana's marriage to Charles.

Prince Charles said his former mother-in-law "will be sorely missed." Prince William said he had his brother Harry "are very upset by the death of our grandmother and we will miss her a lot."

Shand Kydd married Edward John Spencer, 12 years her senior, in 1954 at Westminster Abbey. They had three daughters - Diana was the youngest - and one son.