I kept 3 unfertilized eggs in the nest for a hen to go broody. It took 3 days, then my Cochin sat in there for the night. She got up and left the next day. I kept those eggs in there and it was 5-7 days before she decided to sit. This time she was in there for 2 days before I put fertile eggs under her. I have a hen that lays egg shell inside the egg whites, so I feed them back to the hens.
Now I have to physically lift her off the nest 2-3 times a day to drink and poop(she will poop 1-2 times tops). The poops are human sized and stinky! Bleh! The poor thing wasn't coming out and was looking dehydrated. She drinks 2-3 times a day. I close the door to the coop/nest, so she doesn't run back in. Her legs are weak from sitting. I let her take a dust bath and now she will only poop outside and not even in the run.
I spoil her. I give her HB egg a day, sunflower seeds and oats with starter feed. The more protein the better. So far she's been sitting for 2 weeks. Some of the eggs were 10 days or so developed, so I hope this isn't a problem.
If your silkie is standing over the eggs, she know ls not to over cook her eggs. They will keep on growing. My neighbor that gave me the fertile eggs were cooking without a sitting hen and all doing well. If your silkie is leaving and hanging with the flock, she is not ready.
My Cochin leaves the nest, but stays to herself. She takes a dust bath daily, cleans her feathers and scratches around until I open the door. If she wants in beforehand, she lets me know with a gentle cluck.
Good luck! This is my FIRST hatch and so far so good. If it fails, I'll try again with eBay eggs. I have my eye on a batch. My neighbor rehomed her rooster, do no more fertile eggs.