Ravenous

One kiss is all it takes to lose your soul
Holly Carver is a small-time witch who busts ghosts for tuition money, but ends up wrangling a demon when a haunted house job goes bad. Her Undead business associate, Alessandro Caravelli, suspects the demon is somebody's not-so-secret weapon. The supernatural community is at war, and Holly's unpredictable magic holds the key to hell's doorway. Soon Holly is on everyone's 'must have' list, and not in a good way.
Alessandro wants her for more than magic. A lover with six centuries of experience, the vampire is walking seduction, but he's also a predator. Every moment he spends guarding Holly, every second he spends falling under her witch's spell, he becomes more and more of a threat himself. As Holly's sharp-tongued grandma warns her: vampires are like a box of rich chocolate: they seem so tempting, but over-indulgence is a killer. Second edition. Previously published in 2009 by Signet Eclipse