Silkie x polish? Girl? Boy? Help please
Sexing both polish and silkies is very difficult IMO. But on polish you can normally tell by the feather shape, how red the comb is (not in your case since it's black like silkie) and the hairdo, on polish the female crest tends to stay in a bubble shape where the males get a crazy straggly long crest.
For sexing your bird, I'd say if you can not tell by the hackles and saddle feathers, then you have to watch for behavior. That is a very cute chicken though!