I’m actually disappointed with the twist being “oh you corrupted her with leftover magic” like that instead of being related to her character subconsciously like how people had been suggesting and theorizing to now. There seemed like there could be a lot of potential there but this seems pretty boring compared. Combine that with her not even remembering and it seems like (hopefullly just for now) this isn’t doing anything as far as her character is concerned - for all intents and purposes a new character might as well have shown up.
Tbh, I thought it was obvious that it was Utena's fault since Haruka's new form looked like the one Utena gave her when she stabbed her. So it makes a lot more sense that the reason she is like that is because of Utena.