Do silkies have black skin?
If so it might be really hard to see bugs on it...even if you do part the 'feathers' down to the skin.
I have no experience with silkies.
I assume from your screen name you are in medical school? So I would think that you are familiar with anatomy and deductive thinking. Handle your birds, and do some googling far a chicken anatomical chart, frequently enough to learn about a chickens anatomy...with practice you should become...
If she was broody, I would think she would be 'setting' on wherever she laid her eggs,
or somewhere more 'nest like' rather than on a roost.
Why do you not have a nest that she can get into?