This princess was supposed to marry a prince but didn't want to. She was strong-willed and knew how to fight, or by the end of the book she was fighting. I know there was a lot of mistrust between them. The male thought she was trying to kill him. It was kind of a medieval setting, with castles and dragons. There was a dragon they had to kill. The most prominent thing I remember was this jewel they had to find (not sure if it was crystal, sapphire, or ruby). It went in their forehead and gave them all kinds of power. I believe it belonged to the male, but the female found it and used it and somehow gave it to him. It was how they defeated the dragon they were fighting.

I know it's not a lot to go on, but any help would be appreciated. If noone knows the book, do you know of anywhere that searches for forgotten titles?