Sabin's Servant Cassandra

Here is Cassandra, a character from the book Narcissus in Chains, who is the human servant to Sabin a vampire who rotted himself away to make her happy, because she valued life and preservation of life's blood. He drank animal blood and dead blood, which rotted his body and form. Cassandra is also the werewolf in the triumvirate between Dominic and Sabin, Dominic is the necromancer, and Sabin is Master of the City.
The book is part of the Anita Blake series, by Laurell K Hamilton.