Weirdness of straight norms

Ok dont come for me. Me and my sister were kind of arguing over this. She said that unless proven otherwise, we should assume everyone is straight. And unless told otherwise, we should assume everyone's pronouns are based on what they look like. But I've been misgendered as a male literally almost every day, so if I correct someone i meet, they can't consider it rude. If I look like a guy but I say my pronoun are she/her they automatically assume I'm trans when really I've always been female so wtf. How are you going to assume someone gender when there are androgynous people who you can't really tell, and then go off at them when they correct you.
And then the straight normalcy? Like she was the one who was asking me if I thought a bunch of these celebrities she showed me were gay because I can tell better than she can, and then she's going to complain when I say "Hey is your friend so and so gay?" and she said "Did you just assume her sexuality" like bruh it was just a question Im not assuming anything, but you are assuming everyone you meet is straight?? Isn't that also assuming someone's sexuality?? Make it make sense please.