My mind's been racing a bit and I feel like yeah she'll be an original character crammed somewhere in the story, and probably be antagonistic at first but have an arc where she comes to side with the Kaitoudan. If she is what she claims to be she'll fit the thematic hole left by the original.

(SPOILER)More than anything her introductory quote makes her instantly sound like an incredibly naive rich bitch very much deserving of her own palace. Kinda the anti-Makoto/Haru, a girl who actually profits a lot personally from the twistedness of the adults around her and thus spouts some idealistic bulltrout about how people need to be introspective themselves and trout to discredit the protags. Honestly I hope they go all the way with her and make her impossible to reason with to show how truly evil that kind of mindset can be and not shy away from pointing out that she'd totally defend Kamoshida freely abusing his students.

I doubt it'll play out quite the way I envision it but I'm definitely curious to see where it goes.