I agree with you, as would happen normally, but, now, let me poorly play devil's advocate for a moment.
Perhaps framing it as "bad" is incorrect. However, if we were to think of this in a certain way, it may hold true. Kazuha did everything she wanted to do, due to her desires; those desires sought out people's descent from happiness to misery. That's what made her the most happy. No action was deemed too crazy, unorthodox, nor unethical to get to those results. In a similar way, Yotsuba has done the same. Granted, it was from a completely unselfish desire, to see the one she loved happy, but she wasn't even against killing Uichi's parents or setting up anyone that stood in the way of that desire, if it meant she would succeed. Would that not make her like her mother?