Huh! This is actually a perfect example of the main point. I think you should be able to call yourself whatever you want. If you want to call yourself a girl, why not? As long as we all still understand that the proper definition of "girl" is human female child. And therefore, that in situations where children need to be protected from adults, the fact that you call yourself a girl doesn't mean you are one.
This is where we've gone off the rails I think. I'm not trying to dictate what people call themselves. I'm saying that a worrying number of people have lost track of the difference between calling yourself something and being that thing. And many more haven't lost track of the difference but are afraid to admit that they still know. And so, instead of having a conversation about how to protect women and trans women, we're stuck playing word games that don't help anybody.