By becoming a noble, she also had to swear allegiance to the king. In my opinion she agreed to that far too easily. Noche should have left a demon lawyer with her. In the end, what exactly did she gain? They said she got no land, thus no taxes or other income from estates. She only got a title, but in exchange to that is ever tighter under the king's control. Much good that pesky title will be compared to her healing powers and otherworldly intelligence, sheer magical potential and most of all Noche's protection. Yes, if you ask me, a really lousy deal. Independence would be much better than a yoke with few benefits. They even gave her the lowest possible title.