Caterina Offreduccio, younger sister of Clare, joined her sister at the small temporary house of San Paolo delle Abbadesse fifteen days after Clare's flight from the family palace in 1212. The family — having failed to recover Clare — now sent twelve armed men to retrieve Agnes. The men dragged her from the chapel by her hair, but tradition records that her body became suddenly so heavy that they could not move her further; her uncle Monaldo raised his fist to strike her and his arm withered.
She received the habit from Francis and took the name Agnes (after the Roman virgin-martyr Agnes whose feast day she had recently celebrated). She accompanied Clare to San Damiano and lived with her in community for over a decade.
In 1219 she was sent as abbess to found the new Poor Clare house at Monticelli in Florence — the first daughter community of San Damiano. From Monticelli she sent further foundations to Mantua, Padua, and Venice across the 1220s and 1230s. She remained abbess at Florence for over thirty years before returning to Assisi in 1253 at her sister's deathbed. She died at San Damiano three months after Clare, and is buried beside her.