No fr she had a plan and is going back on it bc a potential war. She only knows the outline of the story so idk why this is making her question everything. Like yeah you didn't read it but no point in worrying. I would just say no and that the dad would still be on his side bc he's the only heir & I'm sure the dad doesn't want another war anyways. Really no need for her to be involved to protect him and his sister. She should just go off with the knight & try to find clues about going back or accepting her new life. Also I hope her brother exposes her (in private) so she can finally decide on what to do since the real one is happy with her bf.
Dear author, just make this webtoon reverse harem..there are 3 men in line (prob more lol) and she cant even reject any of them (/TДT)/