How is Mattie maturing?

In Chapter 19, Mattie takes part in chasing away the thieves that have broken into the coffee shop. When the two men threaten Mattie, her grandfather comes to the rescue with his musket. Sadly, he only scares away one of the men. Mattie, on the other hand, grabs her grandfather's sword and slashes the remaining intruder. In doing this, she proves not only her bravery, but her maturation as well.

Mattie also shows how she has matured when she lovingly cares for her grandfather, who dies that night (one of the intruders tried to strangle him). Though Mattie is grief stricken and devastated, she knows that she will need to rise to the task and carry on alone.