Willy-nilly believer
A careless believer. Someone who hears a statement or story and takes it for granted without considering the implications of that story. In religion, this is the belief in miracles as the multiplication of bread or the belief in an afterlife of a human after having seen the macabre decay of body (and brain). The opposite is an illuminated person who considers the plausibility and the side effects of a story.
There is no sense to discuss this with her. She just believes that she hears the spirits of the deceased talking, just willy-nilly. She is a willy-nilly believer in many things. Maybe she should take a course in physics. Or in psychology.