Silkie Brooding for Months

I have a Silkie I thought brooding with a batch of others so I let her sit. Now the other are not brooding any longer (or rather several others are) and she is still brooding too. We had some mites but treated them all. Beding is stray and pine shavings. They have dirt for baths outside and access to rocks and free range a little daily. Some of the silkies that have feathers on feet were of course hit harder with mites and had more issues but all taken care of now. Her legs look weak but no bumble foot so not her feet. I had to clip her toe nails since she has been sitting for so dang long without going out to scratch about. Her toes look skinny and not strong. Daily I get her out of hen house and put her in the yard to eat and drink. We sometimes give her food and water in her nest but I hate to encourage it. She has eaten strawberries the last few days and stratch and little water and that is about it. She has done this for literally months.

I force her to get out but the other hens pick on her - not bad - but a little and enough to scare her back to her nest inside. When she ruffles her feathers she looses her balance. Her legs shake a little but i think from not using them since sitting all day. She can run when needed. She walks about all fluffed up with wings out to her sides - not sure for balance but that is what the brooding hens typically do. She chirps like a brooding chicken - or what ever you want to call it. I am pretty sure she does not lay eggs and not sure how to check if she is plugged up She poops solid but of course very little cause she eats very little.

She is the only one acting this way - What can I try? -Cereal

I made a small broody pen years ago that I'd restrict them to for a day or two during the day time. Of course don't over expose to the sun. Just some place where she can come around and not be bothered by the rest. A large rabbit cage or something would do. Anything to just get some sunshine and food and water at her leisure. The broody hen does ruffle up and act strange. They're almost feverish about it. They can almost growl at you when you pick them up. You shouldn't leave a broody hen broody too long. Just enough to hatch some eggs and that's it. They don't really eat or drink well when they're like that. So make sure to give her some good eats and sunshine. I like to use a few drops of Ivermectin for mites and worms. Mites can get problematic for broodies too.

My friends have a rabbit cage that they used to "cure" their brooding chickens being that they do not have a rooster and no reason to let them sit. I could borrow that I suppose but I wonder if something else is not going on. She will fly out of my hands and land pretty good but sort of on her face or off to one side. Do you think her legs and feet are just weak from sitting all the time? I get her out and put her in the grass so it forces her to walk a little and to eat. She can hardly get up to the roosting bars or the nesting boxes then. Hopefully it is keeping her active enough to recover.

Isnt Ivermectin for horses? Or for all animals?