His/her brother was a rooster for sure. This one I can't tell. When I tried to get it with the bigger chicks, it got pecked on by my big hampshire red rooster. If it's a hen, any tips on getting them acquainted properly?
Welcome to BYC!
How old is that bird? I want to say it's a pullet but I'm not certain.
As for introducing them properly, I'd read this article
As long as it isn't crowing, I would guess it's a pullet about ready to start laying eggs.