Long time geek, fangirl, mother, and reader. I've got a lot to say, you might not like it all, but it will be honest and hopefully helpful.
First person to display prejudice against Cinder is a Person of Color. Since it hasn't been established in the narrative whether or not Cinder herself is a POC this is a distorted framing of prejudice, in this case an allegory for racism, being perpetuated by POC. UGH!
This is a big pet peeve of mine. Because we live in a racist world, where even readers who aren't white have been taught by mainstream media to default to white for main characters. So when you have POC as the source of racism and/or oppression you're actually feeding into real life racist propaganda that frames racism as something that POC do to themselves and white people as helpless bystanders.
I don't have enough fucking nopes for that bullshit.