The movie '3 Billboards' is a somewhat fictionalized version of the true story. It does a good job of capturing the essence of the real - life situation, like the sense of frustration and the small - town dynamics. But in terms of exact details, it changes things. For instance, the relationships between the characters in the movie might be different from how they really were. Overall, it's more about getting the emotional truth across rather than a literal retelling.
The movie takes some liberties with the true events. It exaggerates certain aspects for dramatic effect. For example, the characters' personalities are more extreme in the movie compared to real - life. However, the core of the story, the mother's fight for justice, is accurately portrayed.