She becomes way too stubborn, and acts insane in the later half of the WN. The MC isn't at fault, the world building is just too rushed and unstable. The Characters' personalities are never clear, they could be a wise and merciful king in chapter 5, but 20 chapter later they turn in to an asshole schemer. There's a lot of stupid things the MC did because she was trying to achieve her goal as a villainess, and half of those things just makes you question her mentality. "The Heroine looks super stupid, but she might be a schemer. The answer was never really revealed and the characters chage way too often.