Her cousin, Eugene Rendu, said wrote of her: "Sister Rosalie’s principal character trait was her common sense, pushed to the point of genius." In 1833 began mentoring the first members of the Society of Saint Vincent de Paul. Among these, Frédéric Ozanam, founder of the "Society of St. Vincent de Paul," and Jean Léon Le Prevost, future founder of the Religious of St. Vincent de Paul, knew well the road to her office. They came, with their other friends, to Rendu seeking advice for undertaking their projects.