Death Hears a Siren — Elizabeth Guizzetti

Norma never chose to be a vampire, but she enjoys her undead life. She runs a profitable cleaning service which assists Seattle's paranormal community by straightening untidy interactions with humans or each other. She loves her work. She and her sole employee, Carlos, have a good rapport. (It helps both vampires and zombies have an affinity for a high protein/low carb diet.)

When three witches on vacation find a dead siren in their houseboat, Norma is called in to clean up the body no questions asked. When the mermaid's family shows up, things really get messy.