I'm glad she's a bit better and that you've identified her problem (or one of, at any rate).
The gene for crest is autosomal (not sex-linked), incomplete (half-expressed if only one allele) dominant; offspring get a full crest if homozygote (both parents crested), and a small crest if heterozygote (only 1 parent crested). So once you've got it in the flock, if you let them reproduce naturally, you're very likely to see more of it.She's also needs a feather cut to improve her vision. Why do people breed chickens like this.