Actually no, I dont understand why but there's 2 versions of this manga, one she was whitewashed after the light spirit blessed her, and the other she stayed the same.
I think that has to do with the artists and translating teams, as you know they have to take the original copy and fix it up before publishing it so we can read and understand it. So I think they’re keeping her the same color as to not let her be whitewashed by the original.
The author made another’s version because people (who read it in japanese/reader in japan) complain about the skin color. So they upload the alternate version. You could find it in mangadex.
I think her skin turn white whenever she uses the light blessing power or whatever and only when she uses it..but since she hasn't used it her skin is her natural color which is nice