Crush called me his “girlfriend”

So my crush and I message just about every day and we go to seperate same-sex schools (our schools are brother and sister schools). One of my girl friends knows a boy from his school, so I decided to start using snail mail from the olden days to send to him (I know it sounds dumb to do it in this era but opening an envelope with a letter is very exciting and surprising). My friend passed my letter to the boy delivering it and told him to tell Richard(my crush) “it’s from Annie”. He’s chill and that’s exactly what he did. He’s in the same tutor class st school with Richard and gave the letter to him, saying “This is a letter from Annie”. Then Richard all of a sudden says “My girlfriend?”

I think it’s a little strange how he says I’m his “girlfriend”, because 1) He does not say “girlfriend” or say he has one, he is known as the smart formal kid 2) He always refers to me through text as “friend” or just by my name

Anyway, What do you think? Also, he has shown (cheesy) signs he likes me. I’m not allowed to date soo this is all secret from parents