YA Horror : A Certain Slant of Light, Laura Whitcomb
"Their mother, in the wings, as often mothers and grandmothers are, ready to catch the children should they need saving, but otherwise invisible."
"I knew that she was trying to save her little girl, but sometimes mothers with best intentions kill their daughters all the same."
Two ghosts, James and Helen, find themselves living in the bodies of two troubled teens. Billy, a recovering drug addict, and Jenny, a bright young girl rebelling against her ultra-religious parents.
The concept is great, but the execution is a bit choppy. I'll probably pick up the sequel though.