You know who would be amazingly feminist?
For one thing, snakes were considered a symbol of women’s power in ancient Egypt. So they have that going for them right away.
Secondly, as per canon, most Slytherins are purebloods with families that are traditionalists. You bet your sweet Muggle butt there are arranged marriages happening. And being traditional, the bride is a dowry and a uterus. Any girl sorted into Slytherin for her ambition is going to be extremely limited (unless she wants to get married and have five kids).
Third, Slytherins get a lot of flack from the other houses in the books. Now there’s some reasoning behind this, but it’s also a lot of stereotyping. Being a person stereotyped gives you a stronger sense of right and wrong, which would lead to the girls figuring out how they’re being oppressed, just for having a vagina.