Ummm.... Not really a question I thought I'd ever want to ask: how did y'all know? Like what let you know that you were a girl?
@spycrab (nb, not a trans woman, but hey since you mentioned us i may as well give my input)
i've always felt less like a human and more like an incorporeal entity controlling a human body. then one night while drifting off to sleep the question just hit me: "do i really have to call myself a man just because the body is?" (a certain quest in warframe may have inspired this, i'd gotten into the game a few weeks prior)
probably would've realized way back in the mid-2010s if i'd been more aware of non-binary people. because there were signs. they were just harder to spot since they were about wanting to be androgynous instead of wanting to be feminine.