The Prettiest Sin in the World(1951)

Original title: Le Plus Joli Péché du Monde

Zoé, a pretty penniless girl, decides on the advice of her neighbor to embark on gallantry. After a brief failure, she meets a young boy, Jacques Lebreton who is about to get married. After causing the failure of this arranged marriage, she will have to play the role of wife of Jacques with his family, until the arrival of the uncle from America.