Maybe I remember it wrong but was it stated that it was a “perfect” fit? It was definitely her size though since it was made magically and specially for her. My guess is since it was a glass shoe and the fact that she must have worked up some amounts of sweat while she danced with the prince, that must have caused the shoe to slip while she ran away due to the moisture from the sweat on her feet 😅.
Ajayi it is a fairy tale maybe the shoe had to come off or the story would have ended differently anyway thanks for sharing your comment