I would say odds are a girl. After nine months, if your silkie was a Roo, I think you would at some point hear a crow by now
I've had silkies for only a year and a half but, if you have other silkies, compare the size, as I have noticed my girls definitely smaller than my boys.
Also notice that my boy silkies have a very pronounced area above their beak and I didn't really see that in your picture.
Here are pictures of my father ( named BoBo) and son (named BooBoo) team. They look bigger to me than the picture you posted so I am leaning toward yours being a girl.
I'm going with girl too. My PQ showgirl cockerel looks tall/gangly compared to your silkie. I agree that her smaller, compact build looks hennish (pulletish) to me.
Welcome to BYC. Glad you decided to join our flock. I'm thinking pullet on your Silkie as well. ) If you haven't done so already, definitely check out our Learning Center at https://www.backyardchickens.com/atype/1/Learning_Center. There is lots of useful information there. Please feel free to ask any questions you may have. We are here to help in any way we can. Cheers.