I feel like she's misunderstanding a lot of things because she feels isolated and unloved. Like maybe her father gave her the sword to protect herself from the "worst criminals" who are also in the prison, in case they try to do something to her. And maybe the prince would have asked her genuine questions and been able to assert her innocence, but her killing herself is almost like a confession that she was guilty. Of course in this new life, she'll obviously act different and wonder why people are caring about her, when they had cared about her before. They probably just didn't know how to talk to her because she closed herself off and focused all her attention on that one dumbass.