This book series, I remember being a trilogy. There was this woman who I believe was a jinn, or something.
She was cast down to Earth and she had to 'connect' with this man, who had earth powers or similar in order to survive. This man and his wife are then killed and she moved in with the guy's brother in order to attempt to find that daughter of the first guy after she goes missing.
There are authorities who know about these powers and I remember them being a fairly common concept. The daughter is then experimented on by an old friend of the cast-out woman, and develops powers earlier than she is supposed to.
I believe it is the second book where the cast-out woman contacts some old friends who tell her that the entity running the 'camp' is someone she damaged immensly who is very powerful and killed at least two known jinns.
In the last book I remember a sort of camp, where children are trained and exploited.