from reading various comments here. Seems to me Cinderella is in fact the exact translation of the author's intent. But it has a bit of a problem in that it's not immediately obvious in English that Cinderella means Ashen Maiden, unlike in Japanese. Also the Disney imagery is troublesome too.Not defending the TL choice to name her that way ( I dont like it either exactly because what you described), but in the Original version from Germany Cinderella is actually called Aschenputtel (Asche = ash, obviously). Puttel means something like dirty (like when you fell down into mud) or in this case working in a dirty enviroment as a cleaner, that gets you covered in dust/ash.
So in a way the name Cinderella would fit 100%, but ofc the citizen of that world dont know the English name of FMC of the Brother Grimms fairy tale.
As a solution, I actually think using another language's translation of Cinderella might be a good alternative, particularly if it's easy to get "ash" from the name, as in the case of the German Aschenputtel. That way we get the meaning of Cinderella, and the phonetic association with ash, without the Disney association.