That is an advanced case of bumblefoot. When it reaches such a state of swelling, it may take weeks or even months to treat it. And the swelling may never fully resolve.
This will require surgery. If you are squeamish, you'd best take her to a vet for it. You will need to soak in warm Epsom salts and then try to dig out all the pus. Chicken pus is solid like wax, and it needs to be scraped out. Then the wound has to be packed with antibacterial ointment and bandaged well to keep out the dirt.
The wound is checked in two days, and it may need to be soaked and more surgery applied if the wound doesn't heal. An oral antibiotic might also be a wise thing.
This will require surgery. If you are squeamish, you'd best take her to a vet for it. You will need to soak in warm Epsom salts and then try to dig out all the pus. Chicken pus is solid like wax, and it needs to be scraped out. Then the wound has to be packed with antibacterial ointment and bandaged well to keep out the dirt.
The wound is checked in two days, and it may need to be soaked and more surgery applied if the wound doesn't heal. An oral antibiotic might also be a wise thing.