My first guess would be a vitamin deficiency. Silkies, in particular, seem to be vulnerable to vitamin deficiencies. I'd get her started on some vitamins. You can either get special poultry vitamins, or use Poly Vi Sol infant vitamins
Another possiblity would be Marek's Disease, as it often first appears as limping. Marek's eventually causes paralysis of the wings and legs.Do you know if she was vaccinated as a chick?
Check the bottoms of her feet, too. Are there any scabs, or are they swollen? This could indicate bumblefoot. Does she act like she's in pain? Any reddness or swelling of the leg?
It might be that it is just a sprain or strain. I'd isolate her from any other birds and keep her in a cage/pen with some deep bedding and no roost. See if just some rest helps her heal.