Dead Wrong by Wendy L. Callahan
Even death doesn't erase the past.
Shiva is a vampire who would rather let go of the painful memories of her past. Unfortunately, a piece of her past walks back into her life in the form of a vampire slayer named Desmond.
Even as they become lovers, Shiva holds him at arm's length for fear of secrets being revealed.
Desmond sets out to understand why Shiva is so guarded and self-protective, and ultimately uncovers all of the details of a murderous plot set in motion by the organization in which he had so much faith.