The Duke will definitely most likely try to force her to do something against her will. I don't trust the nobles one bit.
The kid is so cute, I hope we get to see siblings meeting each other.
I said it before that no matter what her back story was I would still be against her. No matter how bad she has it, it still doesn't justify shitty behaviour. Still sticking to it.
So... the prince killed her because he couldn't break off their engagement and got together with the Saintess. After reading the spoilers, he is trash ML. Japanese authors really need to step up their game and this was a big oof.