In 1815 Rendu became the Sister Servant (local religious superior) of the community at the Rue des Francs-Bourgeois. Two years later the community would move to the Rue de l'Épée de Bois for reasons of space and convenience. "Her poor," as she would call them, became more and more numerous during this troubled time. She worked with the Department of Welfare established by the Napoleonic government, administering a program that provided vouchers for coal and food. She sent her Sisters into all the hidden recesses of St. Médard Parish in order to bring supplies, clothing, care and a comforting word.