How does Scout break her promise to Atticus in this chapter? How would you have reacted?

While Francis and Scout are outside in the backyard, Francis says that Atticus is a "nigger-lover," and that now Atticus will be the ruination of the family, who won't even be able to walk the streets of Maycomb (because of the trial). Scout patiently awaits her chance, and then punches him squarely in the mouth, breaking her promise not to fight.