system
Given the following post, respond as if you're commenting on Reddit:
human
[Cinderella] How comes the shoe only fits one woman?

It's a prince in the story, right? So it's presumably a kingdom they're in (or at least a constitutional monarchy. God Save the Queen) so what about the hundreds of other, probably less Disney-friendly women who have the same shoe size?
gpt
The shoes, dress, her carriage, all these things were created by the fairy godmother especially for Cinderella and so it's not a case of size, but that the shoe is a magical construct that is only for her. 

The fairly godmother is trying to help her, so everything she does is to get Cinderella and the Prince together - so the shoe only fits her and it doesn't disappear and then Prince has a symbol to search for her with.