Although I stuck with the novel after this, the sudden racelift pissed me off greatly, and it is doing so again.
This was a serious misplay on the part of the original WN author. They should instead have done something like a mixture of the two influences, like leaving the skin and hair alone, but changing her eye color. Or maybe, better yet, put a signature on her that had absolutely nothing to do with her coloration at all.
It would have made more sense, since there is no visible evidence on Amelia that made her look out of place in the population. Neither was there such a thing on Claudia's father due to his wind spirit. If spirits leave some kind of evidence on their contractor, then it must only be the Dark spirit that does it via coloration. A 'marking' that any other member of the population might have is meaningless.
If the author had logicked this correctly, then the other contractors might have a stigma of some type, like a tattoo or mismatched eyes. Then Claudia could have received it from the Light Spirit while keeping her tan, which overwrote the Dark spirit's mark.
And for those people jumping up and criticizing other people for 'seeing racism', the author intentionally turned the story into a metaphor of racism after this point, making it clear that this had been their intention all along, so you can sit down, now.