The main character, Angelica, had been possessed by her own guardian angel who had fallen. After the Pastors wife died the Pastor (and/or the followers of this church/cult) wanted a way to bring her back. So they listened to the voice of Angelica's (fallen) guardian angel and used Angelica as a sort of "vessel" for the wife. However ofc, the angel was lying when she said she'd bring the wife back and instead used Angelica's body for herself, so she could walk around Earth as she pleases (or something like that, since angels need a vessel, and fallen angels have their vessels taken.) Forcas had been the only angel willing to help Angelica, seeing that she hadn't been completely possessed (her and the fallen angel were fighting for control of the body). Also the entire funeral for the Pastor was staged, so they could see if the ritual actually worked on her. Just throwing that in incase you didnt pick up on it
SORRY THIS IS SO LENGTHY!! I tried to keep my explanation as simple yet detailed as possible.