Christina inherits only some of her family's favors, but remains on the outs with her father due to being a woman. She seems to fully accept Tic as family, suffers Emmett Till's fate to understand the despair of black people, repeatedly aids the black protagonists, and is clearly quite taken with Ruby in particular. She's also willing to kill everyone to get what she wants. She represents that portion of white women who know and empathize with black people, but still side with oppression when it helps their ends.
Christina's form as "William" looks enough like her to be a gender-flipped version of her, pale blond hair and everything. Except it's not; William was a real person, Christina's old lover according to her, whose form she's copying with the potion, like Ruby does with her own disguise. That Christina would have an affair with a man who looks like a male her is a sign of her narcissism.
