I got 5 blrw chicks last year and only 1 looked like a girl to me. I thought they all were boys because they looked and acted more roo-ish. It turned out to be 1 roo and 4 pullets
I think they were almost 5 months old and i was still feeling confused.
I suggest trying to enjoy them and dont worry about it til you are sure. I think there is still a very good chance that it could be a girl too. My girls looked more boyish than that at that age.