wait... lets say she marries the crown prince and becomes empress. Theres no way the prince won't eventually discover the fact that she's a fake- wont this just be taken as a form of lying to the royal family/treason and end up worse for her and her 'father' in the end? Ofc she doesnt even want to do this but what is that old man thinking making her walk down this one-way road to disaster??
Wait... Even if she married the Prince, they'll eventually do the devil's tango and it's going to be found out that her family has been lying the entire time. Then they'll probably be hung for treason or something.