What is the main conflict in Claudette Colvin: Twice Toward Justice by Phillip M Hoose?

Claudette Colvin: Twice toward Justice is the story of the early life of Claudette Colvin, a fifteen-year-old resident of Montgomery in 1955 who spontaneously refused to yield her seat to a white woman, which violated local law at the time. The importance of Claudette Colvin is that her actions preceded that of Rosa Parks's by nine months.