The idea of forcing students to share a unisex bathroom is actually ridiculous, yes we're all human, but not everyone would be comfortable with that at all, sex in school is a big enough problem enough as it is without making sexes share a communal bathroom
It's all about making kids comfortable, if the girls don't want someone who is still biologically a male using their bathroom then they shouldn't be allowed to, I'm all for making people who are going through personal things comfortable, but not at the expense of other people, there are normally separate disabled toilets around schools, let her use those if she doesn't feel comfortable going into the guys bathroom.