This was very much my experience with the trans girl I grew up with 35 years ago. From the instant she was able to express preferences (I'm talking like age 18 months to 2 years), it was all princesses and dolls and makeup and trying on mom's high heels. We all just assumed she was a gay boy because we had never heard of a transgender person before.

We encouraged her to just keep that behavior at home because she was bullied mercilessly for appearing to be an effeminate boy. But nothing would stop her; she was completely irrepressible.

When in high school, she told us she was really a girl, it was like the most face-palmingly obvious thing. Of COURSE that's what we'd been seeing her entire life. It just made sense. That's just who she is.