This is an important, albeit indirect, question in regard to theme in Stotan!. Of course, Walker is a main character while Milika is a minor character. Despite Milika being a minor character, she is still very important, especially to Nortie.
Let's review the two characters in question here so we can fully understand Walker's meaning. Nortie is Walker's teammate and friend. Nortie doesn't quite fit the jock description even from the beginning. He is quiet, softspoken, and good with children. Nortie is also severely abused by his father in the physical sense. This is where Milika comes in. Milika is Nortie's girlfriend. She is an African-American, and the two are deeply in love with each other.
Walker thinks that Milika has been good for Nortie because she encourages him to be himself, speak his piece more often, and rebel a bit against the racism of Nortie's own father. Just the fact that Nortie is dating Milika means that Nortie is not cowering under his dad's influence. This is important to both Nortie and Walker.
Much is revealed at the dance when both Nortie and Milika arrive with swollen eyes from crying. Nortie's aloofness is misinterpreted, for Nortie has now been severely abused by his dad. Nortie needs emergency room care because of his father's physical abuse. Of course, Walker learns much from this interlude:
Something about the joy and pain of that moment, something about the excruciating contrast, made me feel that no matter what happens now, my life has been worth it. What a ride.