When Cristobal Balenciaga closed his atelier in 1968, Diana Vreeland quipped that Mona didn't leave her bedroom in the villa at Capri for three days.
When she was 74 she married Umberto de Martini who was 14 years her junior much to the worry of her friends . Through her old friend, Italy’s exiled King Umberto II, Mona purchased a title for him and he was created Count Umberto de Martini on 10 January 1973. 1979, Mona’s last husband was killed when the sports car he was driving careened off a bridge Inevitably Mona’s friends referred to the accident as “Martini on the rocks.” His will made it evident that he had planned to outlive her and inherit her fortune. Having told her that he was opening a clinic, he had already pocketed $3 million in a Swiss bank account and made bequests to an embarrassing number of relatives of whom Mona was unaware. She quickly dropped his name and resumed calling herself “Countess Bismarck.”
Mona’s old friend Cecil Beaton visited her at Capri later in life and was shocked to find that all traces of her famous beauty had left her. “She is now suddenly a wreck. Her hair, once white and crisp and a foil to her aquamarine eyes, is now a little dried frizz, and she has painted a grotesque mask on the remains of what was once such a noble-hewn face, the lips enlarged like a clown, the eyebrows penciled with thick black grease paint, the flesh down to the pale lashes coated with turquoise… Oh, my heart broke for her.”
Mona spent her last years putting her affairs in order and making arrangements for various paintings to be disbursed to institutions of her choosing. On 10 July 1983, she died at her house in Paris. She was buried in a Givenchy gown with her third and fourth husbands, Harrison Williams and Count Eddie von Bismarck, at Glen Cove on Long Island.