Wild Sorceress — Margaret L. Carter

In a world where warring nations use magic in combat, years ago young sorceress Aetria's untamed power caused a disaster on the battlefield. Temporarily banished for retraining, she has returned to the army to redeem herself as head of a company of novice mages. She uncovers a traitorous plot by her own commander, renews her bond with her "imaginary" childhood friend, and meets her long-lost twin sister. While also becoming a trusted friend of the commanding general of the army, Aetria unearths secrets of the true nature of the magic she and her comrades wield.