During the Régence of her cousin, Philippe II, Duke of Orléans, she became romantically involved with the Duke of Richelieu, a grandnephew of Cardinal Richelieu. At the same time, the Duke of Richelieu also began an affair with Louise Anne's first cousin, Charlotte Aglaé d'Orléans, known at court as Mademoiselle de Valois. The two cousins, rivals in love, would later both fight fiercely, but separately, for the liberation of the duke from his incarceration in the Bastille due to his participation in the Cellamare Conspiracy.