I guess in cosplaying 'accuracy' is something they take a lot of pride in, but they don't really need to. I mean, my sister is really big into Star Wars cosplay -- she even goes to places like Comic Con and does fund raisers and stuff. She primarily likes to cosplay as the stormtrooper-style of characters. I would point a few things out that she does:
1) She gives herself space for her chest. This is, afaik, not cannon -- I don't even know if there are female stormtroopers in the movies, but I doubt it. So, this is a change in the costume, it's not 'cannon' or whatever, but nobody *ever* has ever, or will ever point it out to her. In all other things her costume is perfect. So, you know, you can change things, and as long as the intent and spirit of the costume is in the right place, accuracy for the sake of accuracy is not really necessary.
2) She makes other changes to the costume that have to do with practicality, and not lack of resources. Things like having more maneuverability, and that kind of thing.
So to dodge the obvious: aren't there enough white characters that you like in The Walking Dead to cosplay is (I don't know if there even is, I don't watch the show), instead I would point out that nobody, anywhere is really going to care if you don't focus on accuracy in this instance. Quite a few people, on the other hand, are going to care if you do. That fact alone should have informed the decision here. It's just common fucking sense. The costume as it is, may be quite good, but it is both insensitive, and really detracts from the overall quality of it. Instead of being able to focus on everything else, you're focused on her face. That's probably not what people are focused on when they see the character in the show or comic.
So, yeah, there's always a way to make the right choice in these situations. I don't think this girl did, though.