I like how she's still dating him despite the deliberate trolling though. That's fairly amusing. The rest not so much.
At what part? The fact that a girl would talk to another person in the girl's bathroom for doing something strange and new? That a human being would show the spark of curiosity to ask questions? The expected negative reaction to having a transperson using X restroom?
Seems pretty typical of human ignorance and curiosity... to the point where I'd expect you'd expect it by now.
Come to think of it, having one's breasts out for whatever reason in a public restroom at all does seem like it's asking for an emotionally draining experience, either from the commentary/confrontations or the looks of shame and/or pity from onlookers. :/