I mean, it's more about the whole "this is a visual sign of the spirit of darkness being involved with someone" thing than a "race," her body was altered a fair bit by the sound of it but it's not like she's a different ethnicity than her own biological parents now or something.
The parallels to real world discrimination in general are obvious and all, but to play devil's advocate I suppose they might have something approaching an actual reason to have concerns here in this setting. Perhaps a history of infamous villains turning up with the dark spirit protection over the years. But even then you get to wonder, at which point did they start creating these threats themselves by treating people poorly over it?