The Devil's Soul - Sister Witches, #3

Hennie never set out to be the villain, but now she's on the run and fighting for her life. The magic she has come to rely on is now a beacon to her enemies. If she can resist using it, she has a chance of staying hidden, but the darkness that she fears in herself is all around her. It's getting harder and harder to witness the evils of the world without stepping in to stop them. Hennie can't hide from everyone, though.
The owner of the body she stole so long ago has awakened, and she wants Hennie gone. She grows stronger with every day, and nothing short of death will appease her-Hennie's and hers.