It's gender neutral btw.
>I'm about 95% sure that if I ask my two school-age daughters if it's weird to address girls and women as "bro" or "bruh"
I'm 100% sure I said women, and not "school-age" girls, who if they weren't your daughters would probably describe you as "creep" because that's what teenage girls do. But sure, go ahead and move the goalposts anywhere you want. If citing teenage girls helps you think you're making some kind of point, then the mic is all yours.
That's actually how it was originally, because in Old English "man" just meant a gender-neutral "person."
Gendered versions were "wer" and "wif", so you could have a "wer-man" and a "wif-man", the latter changing pronunciation to become "woman". I suppose this also means that there are both "werewolves" and "wifwolves".