She was the daughter of marquis Guillaume François de Cepoy and Élisabeth Amaranthe Jogues de Martinville and married count Georges Louis Marie Leclerc de Buffon (1764-1794) in 1784; the same year, she became the lover of Orléans, with whom she had a son, count Victor du Buffon (1792-1812). During the Terror, she helped the legitimate sons of Orléans escape prison. In 1794, she divorced and emigrated to England, where she became a supporter of Louis Philippe.
