From what it looks and sounds like on the video I think she is a Pullet. She sounds too Squeaky to me to be a Cockerel. Most my Cockerels sound more deep like a goose at young age. Maybe someone else can give their opinion.
I handle all our birds; I have found the cockerels tend to be heavier then their comparably age pullet siblings. Do you have pictures of the other birds her age? I am curious to see their head feather with regard to this girl. She has very large head feathers for a hen but I could be wrong. Most of my hens look like bobble heads while our polish rooster looks like Tina Turner with the big hairdo.