I like Sharon.NJ 's idea. You could do any story about her family or the environment that shaped her as a character.

Some other ideas:

Something that takes place during the time of the novel, but outside the scope of your plot. Is your protagonist an infant throughout the novel? If not, and she goes from birth to some older age, then surely you're skipping some time. Pick something that happens during one of the skipped times, but an event that might help shape her as a character.

Something that takes place after the novel, but that still helps you better understand her character, motivations, and choices.

Bottom line, you're just trying to get to know your character better so that you can be solidly inside her head when you're writing her in November.

Cheers,
Michelle