Undead and Unappreciated by MaryJanice Davidson

Most women would love to live as royalty, but Betsy has found that being vampire queen has more problems than perks, except for always being awake for Midnight Madness sales. It may be easy to find blood (yuck) in the dark of night, but try finding a strawberry smoothie. And employees at her nightclub Scratch have been giving her nothing but grief since she killed their former boss. Some people...
But Betsy's "life" takes an interesting turn at a baby shower for her wicked stepmother, who lets it slip that Betsy has a long-lost half sister. Now twenty years old, this woman just so happens to be the devil's daughter...and destined to rule the world.