-  Mother Maddalena wrote in The Princess of Poverty:
But the principal Patroness of the [Poor Clare] Order in France was B. Isabelle, daughter of King Louis VIII, and Queen Blanche of Castille. She always had entertained the greatest esteem and veneration for the Sisters of S. Clare at Rheims, and, at length, obtained the necessary grant from her royal brother, S. Louis, to establish a foundation at Paris. This resulted in the erection of the celebrated royal Abbey of Longchamp, under title of the Humility of our Lady. Four Religious were obtained from Rheims to introduce the new mode of life. Here B. Isabelle, together with a number of noble ladies, vowed her virginity to God. For particular reasons, the rigors of the Rule were somewhat mitigated and special regulations drawn up. Other foundations were established from this place, one of them in London, in 1295. Isabelle died, February 23, 1270, in her fifty-fifth year, and was beatified by Pope Leo.