Ghosts

Susan can see peoples' souls. People dead or alive. She goes on a camping trip with some friends in a place where there are many souls. Dead souls otherwise known as ghosts. There are more ghosts then she's ever seen in her life in the woods where Susan goes camping. Susan has never told anyone that she can see souls, but when the situation escalates she has to tell someone.
***This is in the same universe as 'Now I Know You,' and is about Zach's Mom, but you don't have to read Now I Know You, it'll still make perfect sense.***