She had to flee Cuvilly after the start of the French Revolution and escaped to Compiègne, where the stress she experienced resulted in another illness that took away her ability to speak, and where she received a vision foretelling that she would found a new religious congregation that would eventually become the Sisters of Notre Dame de Namur.

In 1804, Billiart and de Bourdon established the Sisters of Notre Dame in Amiens, where they and other nuns dedicated themselves to the care and education of young girls.

Billiart, who was called "Mother Julie," was healed of both her paralysis and her speech and went on to found schools and homes for poor girls in France and Belgium.

[2] Billiart was admired for her "beautiful embroidery and lace",[2] which she sold in her family's store and donated to local churches and to the nearby Carmelite convent.

She also spent her time making linens and laces for the altar, teaching both poor peasants from Cuvilly and noblewomen from Picardy, and preparing village children for their First Communion.

While in Compiègne, she received a vision about founding a new religious congregation,[6] hearing the words, "These are the daughters that I will give you in an Institute, which will be marked by my cross", which she believed was a "guide for her future".

[3][6] At first, de Bourdon was "repelled by Julie's disabilities and her garbled speech",[6] but Billiart "immediately admired and enjoyed Francoise, who came with a character that was genuine, spiritual and strong".

[6] A small group of de Bourdon's associates, who were "young and high-born ladies",[1] formed around Billiart, who taught them "how to lead the interior life"[1] while they worked generously for "the cause of God and His poor".

[1] De Bourdon rented a home for them, where they lived, prayed, and worked together in a small community; Varin helped write formal guidelines for them.

[7] The foundation was made for what would, under the auspices of the Bishop of Amiens, become the Sisters of Notre Dame, a "society which had for its primary object the salvation of poor children"[1] and was devoted to educating young girls and to "making known God's goodness".

Between 1804 and 1816, Billiart founded 15 convents, made 120 "long and toilsome"[1] journeys, and "carried on a close correspondence with her spiritual daughters",[1] hundreds of which were preserved in Namur.

[1] St. Julie's predominating trait in the spiritual order was her ardent charity, springing from a lively faith and manifesting itself in her thirst for suffering and her zeal for souls.

[8] As briefly reported by Sister Mary Ludvine in the Sisters of Notre Dame of Coesfeld 1952 newsletter, on 30 September 1950, in Mata Virgem, a village in southern Brazil 27 miles from Campos Novos, a 29-year old farmer named Otacilio Ribeiro da Silva was healed of an inoperable tumor by Billiart after the prayers and use of Billiart's relic and picture by members of the congregation who also worked at the hospital where da Silva was brought and by Ludvine, who was the hospital's superior.

[9] In 1952, Mary Verona, an assistant mother general of the Coesfeld Sisters of Notre Dame, who was residing in Rome, was "well connected with the Church hierarchy",[9] and involved in the decades-long effort to canonize Billiart, read the account of the da Silva miracle in her congregation's newsletter.