Streamers want views. Girls get more views. It's pretty simple that she'd advertise it. Girls on the internet get so much shit (evidence: this thread) that I'm not going to resent her for it. Why would you ignore what is (sadly) probably your most marketable quality?
I mean, yeah, I completely deplore a culture in which teenage boys think that the internet is their place and anyone else is an outsider to be shunned. Girls get treated like absolute shit on the internet, so a girl wants to work the system? More power to her.