The convent is so corrupt that Charity and Patience are forced to dwell apart in an outer chamber. Lady Experience explains that she has come to show these things to Katerine to help her understand why her father would not consent to her desire. Katerine then awakens and, speaking now with the voice of experience, advises other young women on how to live virtuously, with specific exhortations to nuns on how to dress so that they will not attract lecherous men. What matters is their inner spiritual lives, not their outward, vain gestures. The shift in voice after Katerine's awakening is nicely handled by the poet as she matures from her earnest desires into the role of sage counsellor.
Nothing is known about the author of the poem.
It could be by a woman, I would think. In fact, it is the nuns' disobedience to the Prioress that offends Katerine most of all so that she leaves the convent in disgust. Although Katerine has a keen sense of hierarchy, she also has good understanding of her personal relationship with God, which helps to sustain that hierarchy. Initially, when her father seems to thwart her desires, she turns immediately to prayer. That defensive gesture is a sign of her good breeding as well as her piety.