Wait Till Helen Comes by Mary Downing Hahn is going to be made into a movie!
"Sanchez Mandryk has penned the script for Wait Till Helen Comes, based on the novel by Mary Downing Hahn, which centers on a 12-year-old girl who's the eldest of three children in a blended family that moves from Baltimore into a house converted from a church in the Maryland countryside. The tormented ghost of a little girl comes to haunt the 12-year-old but forms an intimate though dangerous friendship with her seven-year-old stepsister."
See full article here: http://maxfmedia.com/WTHC.pdf