Blacker Than Blue by Rebekah Weatherspoon

The beginning of Cleo Jones's life as a vampire was the end of her relationship with her first love and only submissive, college senior Benny Tarver. Mutual resentment and heartache have kept them apart for the past three years, but their responsibilities to the sisters of Alpha Beta Omega sorority have held them in each other's sights. With graduation looming, Benny knows it is time for her to move on from the sorority and her lingering feelings for Cleo, but when Cleo realizes she may lose Benny forever to a powerful demon, she must put her fears aside to discover if they can find the strength to let go of their pain and accept that the love between them is true.