They would never know if she was capable of getting angry enough all on her own to attack her husband. Perhaps that was best. She didn't want to know if she had enough rage inside to repeat her attempted murder. One of her greatest fears was to discover that she was more violent and unstable than she realized. Learning about the myriad of ways that Rodolphus fucked with her mind was helpful in dispelling some of her fears, but not all. There was always potential she was as warped and damaged as she thought.