He thinks noone would dare to hurt a princess. It's not his mother who is a saint. He just thinks that the princess would never have to go through things like that.
Can he let her free for like idk 2 or 3 years ?? plus she needs time to sort out her feelings for him. It's just sad that she's going to tie the knot with him without being able to do what she wants...
she be like "he kissed me so passionately..." *blushes* to "aha! it's just animal instincts!!!"