I remember reading this in a college English Class about 20 years ago. The elements I can remember are:

 1. Cinderella's mother was killed by the king because she was a witch.
 2. Both Cinderella and her mother had Red hair, this was a sign that they were witches.
 3. Cinderella used ashes in her hair to hide the fact that it was red.
 4. Cinderella planned to kill the prince in order to hurt the king. (Revenge)
 5. Midnight is significant in that it is the witching hour.