Mate Forsaken by Beth D. Carter

Circe and Miles had grown up together, and they knew they were moon fated mates. When their pack went to war with another, many people lost their lives, including his older brother. To end the conflict, the two packs decided to unite through marriage. Suddenly thrust into the alpha heir role, Miles feels he has no choice except to do his duty.
Circe is devastated when Miles asks her to stay with him, despite his upcoming marriage. Unable to watch Miles mate another woman, she leaves.
Fifteen years later, he finds her again when she accepts a teaching job in the Sheridan Pack. This time, he is determined they will be together no matter what. But, can she forgive him? Can she truly believe him when he vows she is his everything?

If not, what does he have to do to prove his love for her?