Princess Antoinette had a long-term liaison with Alexandre-Athenase Noghès, a Monegasque-born attorney and international tennis champion, in the mid-1940s.

Having divorced Noghès, she and her lover Jean-Charles Rey hatched a plan to depose her brother Rainier III, Prince of Monaco, and declare herself regent on the basis of having a son who would one day inherit the throne.

[3] Rainier's marriage to Grace Kelly in 1956 and the arrival of his heirs, Princess Caroline in 1957 and Prince Albert in 1958, effectively scuttled Antoinette's plans.

[4] She was the president of Monaco's Society for the Protection of Animals and Refuge[3] and a patron of the UK-based Battersea Dogs and Cats Home.

She is buried in the Chapel of Peace in Monaco beside her parents, her daughters Elizabeth-Ann and Christine Alix, her last husband John Brian Gilpin and her nephew by marriage, Stefano Casiraghi.