Safe by Jenny Zink

This story is about a girl that can walk in other people's dreams. If the dreamer is in danger she gets pulled into the dream. She is then able to save them from an infinite sleep. This time she's pulled into a completely different dream, involving angels. Also she starts to get very odd visions. She meets a boy who seems very nice, but in reality, it's just a facade. Excitement leads to danger as an angel's story starts to unravel.