@maitawa:
Er, I don't know if you've been paying attention to the whole "villainess" sub-genre, but opening with dramatic-fiancee-breakup-over-ostensible-bullying is just any old Tuesday in shoujo-isekai-land these days, and this is as utterly generic as it gets (like, my eyes sort of glazed over at the description of how their breakup came to be). As these things so often go, regardless of ultimate origin, any one person is not stealing it from any other one person in particular at this point, having become more like something floating around in the collective fandom conciousness. ~w~;
(The "twist" here is a relatively inspired mash-up of the engagement-annulment plot and "I wanna learn magic" (usually-)shounen isekais
via a (prospective?) yuri couple between their respective protagonists. Not exactly likely to become a literary masterpiece, but potentially extremely fertile ground for good dumb fun.)