She was born Judith de Marffy-Mantuano in Hungary. In 1926, she won a scholarship to study economic history at the London School of Economics, where she met Billy Hare, the future 5th Earl of Listowel. The couple were ill-fitted, they travelled around Europe together and separately for the rest of the decade. After war was declared, Lady Listowel urged both Count Ciano, Mussolini's son-in-law, and her kinsman, the Hungarian prime minister Paul Telecki, not to side with Hitler.
Beginning her career as an author in the 1920s, Lady Listowel produced a volume of short stories about Hungarian society, as well as other works including: This I Have Seen(1943), which was an account of her early life, Manual of Modern Manners (1959) The Modern Hostess (1961), which attracted widespread attention, The Making of Tanganyika (1965) and Dusk on the Danube(1969).
She died 3 days after her 100th birthday in July 2003.