Well it could be that the change of fate does not stop the history from repeating itself. She could have lived , not be sacrificed, died of old age and she reincarnates into a new cycle anyway. I mean the MC repeats the cycle as well.
Karen is insane, not really obsessed. I mean she tried getting the library location and almost gave up when the library didn't spawn. I don't think she is that obsessed.
Gardevoir might be a candidate for pure evil in place of angie. She also could be a guiding force for the prophecy like Spatia, Tiempa and Madame X. But with how little she appeared it's hard to say.