The answer is
This is information on the "Pitch Letter" by V.C. Andrews. In my opinion it was not supposed to be revealed but many thanks to simonsays.com/VCAndrews the pitch letter and many unanswered questions on whether or not "FLOWERS IN THE ATTIC" was based on a true story can now be revealed!
Lies, Lies, Lies.... all based on a TRUE STORY?
YES!
And here is the evidence
[Click here to view the actual Pitch letter.]
It is a very hard document to read so I will give quotes from the letter if it was too small for you to understand.
Dear Ms. *******
Using a peo name, I have written and sold without an agent, three Gothic Romances, before that I wrote confession stories.
All the while I was writing other tales ... one kept bearing hard on my mind, begging to be told.
This is the fictionalized version of a true story. Real children who struggeled to survive under almost undurable circumstances. A horror story.
I call my novel, which is not truly fiction... Flowers in The Attic.
Yours Sincerely,
Virginia Andrews
(That is not the last name she signed it with but I could not make it out)