Wait, she was able to have a human-like appearance even before the priest found her? So the priest wasn't the one who gave her the crown of thorn that allows her make her look more human?
@Sancturil I may be wrong, but I think the priest was the one to give it to her. She can naturally look human too, she only needs the crown of thorns when she gets out of control/too emotional. It forces her back/to calm down.