Hot tweezers and a needle....squeeze all the puss out and then keep it clean. Chickens are tough birds but I would keep an eye on the redness and swelling. Once its cleaned out completely you can use contact (eye) solution to rinse it and sugar to prevent bacteria from growing. Rinse it at least...
I have 5 indoor/outdoor chickens. 1 EE Rooster and 3 EE and an old Rock hen.
They come inside to roost at night and go out during the day unless the weather is terrible then they remain indoors.
I constantly clean my floors but other than that they are wonderful pets. Very intelligent and well...
I'm not an expert but it seems like a build up of fluid and should be drained and cleaned. If you can I would take her to an avian veterinarian to get looked at if you haven't already.
Is the swollen area soft or firm?