There are two previous Cinderella stories which are both grotesque to say the least. In one of the versions, written in the 17th century, Cinderella kill her evil step-mother by slamming a lid of a chest on her throat which breaks her neck. In Brothers Grimm version, the step-sisters chop off their feet to fit the glass shoe. When this trickery is uncovered, the little birds that follow Cinderella around, peck the evil stepsisters’ eyes out.
https://www.scoopwhoop.com/entertainment/disney-fairy-tales-with-dark-twisted-endings/
I knew I heard of the one where they cut their feet. I just thought the dark part was something about her not having a happy ending.