Deadly Little Mermaids

Low Campbell, ex-cop, private detective, and mermaid, has been offered a job that she can't turn down. Titus Hawthorn, the city's oldest and most powerful vampire, wants Low to protect him from an even older and more powerful vampire, a man known simply as the Count. The Count gives Low forty-eight hours to find someone that's been around as long as he has, someone that can amuse him, otherwise he will kill Titus and another one of Low's friends, a mermaid named Savanna.
Not only does Low have to contend with the Count, who just happens to be the world's oldest vampire, she has to contend with a fireball throwing elf, cops that keep shooting her in the stomach, her human boyfriend's boss, who thinks that he should dump her, and her arch nemesis, a siren that wants to steal her treasure.