|Saint Isabella, at a|
church in Paris
She became attracted to the mission of the Franciscans, and by special dispensation of Pope Innocent IV, she was allowed to have Franciscans as her confessors, rather than regular priests. She was very devout, and took special interest in applying her embroidery skills on priestly vestments. Once, while making a nightcap, her brother the king asked for it. She said "No. This is the first of its kind and I must make it for my Savior Jesus Christ.” She finished the nightcap, gave it to a poor person, and made her brother another,
As devout as she was, however, she was still a royal princess, with obligations beyond what most daughters experience. She was betrothed to marry Hugh, the future Count of Angoulême and of La Marche. Isabella was determined to remain a virgin, and so said "No" and would not carry through on the wedding plans. Unable to secure an heir, Hugh looked elsewhere. (This did not cause harm to the relation between the two families: Hugh later joined Isabella's brother Alfonso on the Seventh Crusade, where he was killed in Egypt.)
Later, she was betrothed to Conrad IV of Germany, son of Holy Roman Emperor Frederick II. Politically, this match would have been more impressive than the one with Hugh, and everyone thought it a good idea, even Pope Innocent IV, who entreated her to agree to it. But Isabella said "No" again. She explained to the pope that she wished to live a religious life, though not entering a religious order, and part of that involved remaining a virgin.
Isabella asked to be able to found a monastery of Poor Clares (Clare was the sister of Francis of Assisi). Sanction from Pope Alexander IV dated 2 February 1259 shows that the Monastery of the Humility of the Blessed Virgin was completed by that date. Isabella lived in the monastery, but apart from the nuns' cells. Offered the position of abbess, she again said "No": if she were abbess, she would have to give up the riches available to a royal princess, and would not be able to support the monastery.
After her death and burial, her body was exhumed after nine days and observed to be uncorrupted. That, and the reports of miracles happening at her grave, caused her to be declared a saint. Her feast day is 23 February.