YA Fantasy read in high school in 2011 more info in comments

[Jessica]

This one specific scene I remember: the one who captured her realized that she is invisible to most of his camp. He makes her walk around naked to attract the ones who can see her so they can guard her. As they start running at her, she's able kill most of them one by one. Another scene: as she is kept in the leaders tent, he takes new girls to bed with him unwillingly. The captured girl lays on the floor of the tent and consoles the girls after he's done with them. The captured girl is one of two protagonists in the book. The other is man who searching for her. The girl may be of a royal bloodline but I'm not positive.