In 1778 she entered a house of the Sisters of St. Joseph, which had just been established at Monistrol (Haute-Loire) by Bishop de Gallard of Le Puy.
She and her sisters established a hospital[1]^ At the outbreak of the French Revolution she and her community followed Bishop de Gallard in refusing to sign the Oath of Civil Constitution of the Clergy.
She returned to her father's home, and was soon imprisoned for 11 months at Saint-Didier and only the fall of Robespierre on the day before that appointed for the execution saved her from the guillotine.
[2] In 1807, Fontbonne was called to Saint-Étienne to assume responsibility for Les Filles Noire, a group of 12 young women and members of dispersed congregations.
[1] She went to Lyon to find and purchase property to build a motherhouse and novitiate on rue des Chartreux.
This began the expansion of numerous congregations of the Sisters of St. Joseph in the United States and Canada.