The sculptor Daisy Boyd, was found dead at the Nightingale Psychiatric hospital in London on Thursday.
Boyd was engaged to publishing heir Dan Macmillan and was also the granddaughter of Rose Gray, the late co-owner of Michelin star restaurant the River Café.
A family friend told the Daily Mail: “Daisy died on Thursday morning and all her family and friends are devastated by this tragic news.
“She was just 28 years old and we are all deeply pained that she has died so young. Daisy was a brilliantly vibrant and joyous person who lit up any room she entered.
“She had an infectious enthusiasm and has been cut off in the prime of her life.
“Enormously popular, curious, generous and with a diamond sparkle, she was greatly loved by her family and friends, and the gap she leaves is, at the moment, unfathomable.”
The cause of death is still unknown.
She was staying at the hospital in the treatment of eating disorders, addiction and other mental illnesses.
The hospital said:
“Nightingale Hospital sends our deepest sympathies to the family, but we are not in a position to comment owing to the delicacy of the situation and out of respect to the family.”
The artist was engaged to Dan Macmillan, the 42-year-old great-grandson of Conservative Prime Minister Harold Macmillan and heir to a £300m publishing fortune. However their engagement seemed to have ended in July.