This is my opinion only. But I believe the reasons that Evil Queen from Snow White and Lady Treamine from Cinderella mistreat the titular characters is different from the in-story explanation.
Evil Queen used the fact Snow was pretty as an excuse to get rid of an heir to the تخت which I presumable that the Queen was ruling for Snow.
Lady Treamine's daughters might be older سے طرف کی a few months in the animated Disney movie. And back in those days older daughters were suppose to marry before younger ones.
I don't really have a reason for Edward's step-mother, Narcissa. But I assume that the Kingdom is suppose to be run mostly سے طرف کی a Queen?