Here, that would be a duck that would be getting some sort of surgery to excavate the puss, and necrotic tissue to allow proper healing. Given how large the swelling is around the area, having a vet perform such a thing may prove to be quicker, and overall more effective, they'd also likely give you an NSAID for her, for pain, but if you want to try it yourself you could.
I would first start off by soaking the foot in a water mixture of either Epsom salts, or an antiseptic mixture such as betadine, or chlorhexidine. Massage the area while she's in the bath. Do that however needed until you have the eschar/scab loosened up a good bit, then you should be able to peel the eschar off with not too much resistance. Keep soaking, and try to massage out as much as the puss in the swelling as you can.
When she is not in the bath, she should have an ointment applied to the area, gauze wrapped, around, and bandaged to prevent bacterial contamination of the wound and to provide cushioning to the surgical site. Some folks use what's called Tri-cide Neo for better antibacterial penetration into the sore. A DMSO gel diluted half-way down with water may be applied to the area to reduce swelling, and pain.
https://www.backyardchickens.com/threads/duck-feet-bandages.1424682/
Depending on how it looks after surgery, it may be good to use an antibiotic, such as cephalexin, to kill any bacteria you weren't able to reach.
https://www.chewy.com/fish-aid-antibiotics-cephalexin/dp/185208
Bumblefoot or "Podermatisisis" can be brought on by several factors including malnutrition, uneven weight bearing due to other illnesses, but most especially, hard/unforgiving bedding that promotes erosion of the plantar surface, causing flaking, allowing bacteria to penetrate inside. That process mentioned is increased with a bird-like Pekin, due to their heavyweight. Ensuring birds feed is formulated to her specific needs and understanding environmental needs are crucial for treatment, and further prevention of the Bumblefoot.