Oh, little Joey. We just want to snatch her up, give her a hug, and put her in our pocket.
Joey is the youngest Watson, and she's definitely the sensitive one of the bunch. She feels bad for everyone—even Byron. In fact, she is so determined not to let Byron get hurt that she blows out all of Momma's matches the day Momma tries to burn Byron. Yep, she's risking life and limb for this troublemaker. And she defends him so persistently that Momma eventually gives up.
For all of her goodness, though, Joey can still be an annoying little sister. She always follows the rules, which, let's face it, is a little irritating. She's a bit of a tattletale; but to be fair, most of the time, she tattles to keep her brothers out of trouble rather than get them in trouble. At heart, Joey just wants everyone to get along and be happy. In return, Joey's family showers her with kindness—again, even Byron.
We're guessing it's no accident that it's Joey who almost dies in the church. Joey represents goodness and innocence: she's kind and polite and protective, and she never wishes harm on anyone. When the men set off the bomb in the church, they do it because they are angry about changes like the integration of the schools. They hate the vague idea of any African American children going to school with their white children. But are they thinking about the individual girls like Joey? Or the other girls who die in the church?
The author wants to make sure that we pay attention to the specific children who die in this attack. Each of the four girls is someone else's Joey, someone else's daughter or sister who is good and innocent and beloved. To help us understand how terrible this event was, we need to understand how devastating it would be for the Watsons to lose Joey.