Shattered Souls by Kris Ruhler

Stand in the line of fire or embark on a dangerous mission? Khara’s choice is to escape. But where can she go when her worst enemy lurks within?
Khara, a teen soldier in the Mythren army, yearns for freedom. Faced with a moral dilemma, she takes a stand, defies the army’s rules, and stands in the line of fire. Literally.
So when a high-value scientist is taken hostage, Khara joins the rescue team and leaves the Compound. Little does she know about the dangers that lurk in the forests and mountains: beasts, bandits, and a strange stalker who’s sabotaging their mission.
To top it all off, Khara’s biggest enemy is…herself. During bouts of memory loss, another being surfaces from within her—a fierce, ruthless warrior. One who won’t hesitate to hurt the people Khara cares about.
Belor, the kidnapped scientist, is the only one with the cure. The race is on to find him.