I'm sorry, what?
So in the original game, she marries the prince, and then the prince fucking sends her off to some random dude, his own wife??? (I assume after the protagonist of the game makes him fall in love with her or whatever.)
I know details must be lacking but it sounds like we got a super evil prince here. I mean the 'otome villainess is engaged to the prince but blah blah blah then she has a horrific end to her life BAD ENDING' is a normal thing but that's usually due to the engagement being cancelled, in this case they actually got married???