in the kind of situation and context despicted, how could the butler guy NOT force her to stay, she is waaaay too valuable to be let go, and as she already turned down the prince, he has to find a way to make sure she stays. It is underhanded, not a nice way to do it, but it could be a lot worse, at least she is given nice food. Youall really not think, romance is secondary, you have a live human threath detector in front of you, the prince just tries to make her like him, as he likes her, but that and her new forced job are two different things. Its very naive to think that just because she doesnt want to they will let her go