How is the old woman changed at the end of the story in wife of bath?

Near the end of the wife at bath's tale the knight is disgusted with the woman due to her age and looks which prompts a speech from her about how grace and nobility are gained through character not something your born with and she gives the knight a choice to have her, an unattractive, but extremely faithful and loyal wife or a beautiful wife that he cannot trust--- the knight tells her to decide for him and she turns into a beautiful young woman