Vampire Battles by Joe Smith

When Gustav turned a second woman into a vampiress, he started a chain reaction which could only end in one way. The two women who shared his blood, and therefore shared a deep love for him, had to confront each other. Neither could be happy while the other was still alive. But before they could fight each other to the death, they both had run-ins with an order of priestesses who hunted witches. As the church did not recognise vampires, these priestesses saw them as witches who had changed their form. It was their duty to kill these witches.