Which character in Fever 1793 changed the most?

Matilda (mattie) cook

Explanation:

Fourteen-year-old Matilda "Mattie" Cook is the teenage protagonist of a young adult novel. This means that over the course of Fever, 1793 she's going to be coming of age, searching for her identity, and learning what it means to be an adult. We mean, come on - that's just what teenagers in young adult novels do!

As the fever starts taking its toll on Philadelphia, Matilda's life is changed for the worse.