Daisy Boyd, 28, was found dead at the Nightingale Hospital in London on Thursday.
Boyd had previously been 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.
The circumstances of her death are currently unconfirmed.
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.
“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 friend said the family wished to grieve in peace.
Boyd was staying at the private Nightingale Hospital in Marylebone, which specialises in the treatment of eating disorders, addiction and other mental illnesses.
In a statement 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 previously engaged to Dan Macmillan, the 42-year-old great-grandson of Conservative Prime Minister Harold Macmillan and heir to a £300m publishing fortune.
The pair’s engagement reportedly ended in July this year after three years.
