She previously wrote about her decision last week on tumblr -- urging fans "If you are in the position to cut off 8 inches of your hair, then I strongly urge you to do it. There are so many human beings out there who would LOVE the opportunity to possess long hair, but simply cannot because of their current situation. Let's share!"
In the movie, Woodley plays a 16-year-old living with cancer.
Check out a pic of Shailene holding her freshly-cut hair below: