Petals on the Wind by V.C. Andrews

For Carrie, Chris, and Cathy, the attic was a dark horror that would not leave their minds. Of course mother had to pretend they didn't exist and grandmother was convinced they had the devil in them. That wasn't their fault, was it? Cathy knew what to do. She knew it was time to show her mother and grandmother that the pain and terror of the attic could not be forgotten. Show them, show them once and for all. 
Good condition, loved, soft cover. Pocket Books.