You know what I just realized? This is how you have someone go traitor. She's basically got unfettered access to the Prince, could just turn a blind eye in exchange for getting her and her family to join another country, and bam, she's out of the contract. Doesn't matter if the king of some other country (that your country is either at war with or fighting secretly) says that you owe them money, you don't answer to them.
While it might be funny, this is an incredibly dumb way to go about things. She saved the Prince's life, confirmed his potential, stole his heart, and you repay it by treating her like an enemy and putting her into a legal prison situation where she is required to die should she need to? Fucking hell, she can just pretend to sneeze at the right time and not notice an assassin as he sticks a knife in the prince, and with how you treated her like a freaking enemy she'd have plenty of motivation to do just that. Talk about shooting yourself in the foot just to say you won.