crowing is VERY rare in hens. I've seen a video of a hen crowing. But honestly, how many people here have chickens... and how many of us have a hen that crows? Yeah, it's just not likely to be the case. If your bird is crowing, I'd bet money on it being a rooster. Did you say how old your bird is? It does have the crest shape of a pullet, BUT--- a lot of my boys start out that way too. I could probably post 3 birds right now that I'm sure are boys and they look as pretty and round as a girl. If you have nicer quality silkies, they are going to look more girlie and be harder to sex. That's just the way it is. Especially if they are under 6 months, they will look girlie. For example-- this particular rooster is now a year old-- but this is his 5 MONTH old photo. This is a HUGE difference from what he looks like now: 5 months:
and at 7 months-- his comb is finally getting bigger, but still a girlie looking crest:
And what he looked like earlier this Spring: finally he has the full blown boy crest
These are all the same bird. The first picture -- there is a tiny comb there. That dark spot is part of his splash coloring in his crest, makes it look like his comb is bigger than it is. Often they don't grow their combs in until later. But when his comb started growing-- it really took off. But the nicer quality boys do tend to look really girlie for several months.