It's true that having female friends and fiercely disliking football lad culture aren't something I'd consider to be indicators that someone is a trans girl, but they were unusual enough at the time that they helped generate a sense that something was up.
i wanted to come back to this. Because further reading shows that it was in Europe/UK in the late 80s and 90s. Which is exactly when i was a teenager who rarely wore dresses and make up, loved football and "scrambled over tanks" a lot (military kid)
it didn't make me a) unusual or b) a boy.
Neither did my penchant for heavy metal and docs. Alsongside steak and beer
As it happened at that time bands like Japan and Duran Duran and people like Adam Ant and Boy George (who pre-singing fame had a fantastic look, i remember him being interviewed in Cosmo about it. I read Cosmo because i like looking at fashion and i was at a girls boarding school so it was always lying around.) oh and Steve Strange! Blitz Kids were a thing (I spent time in London at weekends, and that was when i finally got into makeup - borrowing eyeliner from my boyfriend!)
Even some of the younger soldiers who came into the NAAFI bar where i worked the summer i left school would wear a bit of eyeliner when they were off clubbing in Hamburg for the weekend. None of them were women. The very idea that they might think they were women for liking Japan, clothes, make-up and only doing the bare amount of sport to pass the annual fitness test would have made them laugh.
Gender non-conformity doesn't make anyone the opposite sex. Jeez - even Freddie Mercury behaved like a manly man a lot of the time. In nail varnish.