I've heard silkies are really hard to sex, even at 5-6 months. You'll probably just have to wait it out.
at the age this chick is, it could still go either way, but so far it looks girly. With the bearded silkies I tell folks don't count your hens until they are 4 months old, especially if the chick is from a decent breeder and not a hatchery. Watch the chick as it roams around and interacts, does it stand tall with neck and head high? or does it stay more horizontal and even carriage as it walks around? really tall and head high is more indicitive of a boy, lower even carriage is more a clue to being a girl, but it isn't 100% by no means.
