Not that she planned to let him get off that easy. Once he was finished messing himself, she intended to point out in excruciating detail how much he reeked and take him to the nursery to remove his dirty diaper so she could bathe him.
She intended make him feel guilty about his helpless incontinence for same reason that doctors make their patients feel guilty about their illnesses, i.e., guilt makes the subject more amenable to control by an authority figure. Her plan called for him to regress both emotionally as well as physically. By the time she was finished with him, she intended that he would have willingly surrendered himself in body and soul to her will.