I read a book a little while ago and I am trying to figure out the name of it. It was fiction and that much I know.
It was about a girl and her mother in the real world and unlike normal people they survived on walking through people's dreams. The girl's mother had told her to stay out of sight and never walk through someone's dreams more than once, also that for trying to find the way out of the dream is to go where the birds go.
The girl and her mother had recently gained new neighbors and there was a young boy her age. She walked through his dreams once or twice and they started to like each other. When the girl's mother had been kidnapped by someone, the girl did everything to find her but she also had to keep her head down and run from the police who were after her and her mother, she was, I believe, put into a mental asylum where the boy had helped her to escape.
Although the boy who is her neighbor found out what she really does, so she continues to go hiding but at a gas station she went to the bathroom and somehow transported through mirrors into the dream world/city. She also found out that her and her mother were not people from the real world, they were based in a dream.
She also found out in the dream city a boy who helped her find her mother and the dream city and that the king or leader of that dream city was, in fact, her father.