In the original story it was a masquarade... :)
And how is she the only one in the entire kingdom with that shoe size?
Well, the magic glass slippers were molded by the faerie godmother to only fit Cinderella's foot perfectly
If it fit perfectly how did it come off?
Well, because it all was part of the Faerie Godmothers plan!
I mean, she wanted to hook up Cinderella with Prince Charming, otherwise she wouldn't have helped her.
It was all just a conspiracy
She was probably covered in more makeup than lady gaga.