For some reason, it feels like the new guy is a girl or something. Or maybe her brother.

We can put them both together and it is her cross dressing sister...?

I like both ideas of where you're going with it, but she herself hasn't crossdressed yet. Maybe he crossdresses into a girl or he himself is interested in crossdressing boys like the main character girl. Or he is just a plain old crush that is fine with her tastes.