Here is a picture of our little splash (left) and a young roo. I feel more comfortable leaning pullet with ours after comparing body shape and posture of the roo on the right.
I would guess all hens, most of my silkie roosters get a bump/knob on their comb by that age. The flat combs still makes me think they're hens. Streamers came in way later for my rooster and sometimes hens just have longer hats.