Tale of a Body Thief by Kristy Centeno 

Her special abilities can save lives, but so can they kill.
Rovena Silvex has hunted and eliminated dozens of demons throughout the ten years since her initiation as a hunter. Possessing supernatural skills only makes her job a lot easier.
When she’s asked to visit the county morgue to look over a deceased victim and find out what demon killed him, the body rising from the dead is the last thing she expects.
Now Rovena is stuck with a walking corpse and no answers as to how he managed to return to the world of the living. However, the victim has changed and the more time she spends with him, the more she realizes that what crossed over might not have been the soul of the dead man but something much worse.
Complications arise when her new assignment is targeted by demons hell-bent on making sure he stays dead for good.
Killing demons has always been a piece of cake. Keeping one alive however, is a whole new ballgame for her. If she fails, she risks setting in motion a war between heaven and hell. But if she succeeds, she could trap a powerful Lord in a world he doesn’t belong in, forever.