Your silke is broody (hormonally driven to hatch the egg) - silkies are notorious for going broody (many keep them for this exact purpose as they can put eggs from their other breeds under them and have them hatched out).
Do you have a rooster? If not, the egg is not fertile so there is no chance that it will hatch and you should remove the egg to avoid a rather nasty, smelly mess down the road. Do not, though, eat the egg as after four days of setting even an unfertilized egg is not at it's best for consumption.
If you DO have a rooster you can choose to allow her to set the egg and see if it hatches or remove it if you are not wanting to have a chick at this time.
If you don't have a rooster but DO want to have chicks you might want to ask around in your area and find some fertile eggs to slip under her (remember to remove the egg she has now) and have her hatch those out.
