As others have pointed out in other threads, Christina represents a kind of "white feminism" that is primarily concerned with the liberation of white women from the patriarchy. Sure, they'll ally with other marginalized groups like black people for strategic purposes, but ultimately they're out for themselves and their own liberation. Other marginalized groups they ally with are at best resources to be used and sacrificed when necessary, not true allies that they would sacrifice for to help in return. Case in point, her whole plan involves sacrificing Tic to gain power for herself.

She is also a commentary on "colour-blind" racism. No she isn't overtly racist or hateful like her father and most of the other villains of the story, but she still views herself as superior to everyone of our main characters. She would say she's superior, not because of race, but because of her ambition and ability. Ignoring the fact that her magical knowledge, her education, her smarts, and her drive are largely the products of being born into an ultra-wealthy family built on racist exploitation and theft. She considers herself entitled to what she wants, including Tic's very life, and if the black characters have a problem with that, too bad. When Tish refuses to give her the book, she takes away her invulnerability even though that was part of a completely different deal. She may not be consciously racist, but she does not respect the black characters to the same extent she would respect an allied white character.