Souls of the Damned — E.S. Moore

Innocence is relative, and evil is damned hard to kill...

Kat Redding would love to take a break from the gruesome, dangerous work of hunting down rogue vampires and werewolves, battling for innocent lives. But there's no peace for Lady Death. Until Kat's young charge, Sienna, appears on her doorstep, escaped from the shadow-paradise of Delai. Sienna is weak, confused, desperate--human in the utmost. If Kat is going to have any hope of breaking the hold of Delai, she'll have to infiltrate the walls around the false sanctuary. And the only way she can do that is to trade in her battle-hardened, bloodthirsty vampire's body--for Sienna's human form.

With no weapons but her wits, Kat has to trust a demon, defeat an angel, and wrestle with her own rebel soul--because with all the fear and death she's conquered, no one has ever offered her another day under a warm yellow sun. . .