Darkwind (The Starchaser Saga Book 1) / Renee Dugan

The Middle Kingdom of Talheim has enjoyed peace for decades. But with the threat of war rising from the ruthless South, the dream of a quiet life is fading. And for the noble but naïve Princess Cistine, that means embarking on a dangerous quest to the Northern Kingdom, where she hopes to forge an alliance against their southern foes and save her people.

But when Cistine is captured by an outlaw and his band of cutthroat warriors, she finds a more deadly adventure than she bargained for - and a greater power within herself than she ever knew.

Swept up in the unpredictable tide of a tenuous and shadowy political climate, a ruthless land governed by the stars, and the unexpected revelations that come from her mysterious new companions, Cistine must learn how to fight, how to lead...and above all, how to trust herself. 

If the young princess can't be forged into a fighter, then her kingdom will fall.