One of my best friends strongly believes that there are two genders even though a few of her friends are non-binary (including me.) What can I say to convince her that there are more? She misgenders one of our close mutual friends and he feels social gender dysphoria because of it. He goes by He/They pronouns but she refuses to say he and it took her a long time to use his preferred name even once. I tried to use his discomfort as a reason to get her to at least respect them but she doesn't like talking about it. I don't get dysphoric but it still bothers me.
P.S. She's cishet and not an ally.