It's a good start. Stay with her while she's soaking to ensure that she is not drinking the water. Epsom salt WILL give her runny stool which could result in dehydration if she were to ingest it.
After her 15 to 20 minute soak, rub the foot gently yet briskly with a 'spent' terrycloth rag working from the leg down towards each toe; you're hoping that the nap of the rag will catch an edge of the softened skin at the bumble site and opening it up, eliminating the need for a scalpel. Sometimes, you'll need to soak her daily before getting the desired result, so don't be discouraged if you can't get the wound to open in one or two soakings. If/when you should get so lucky as to have the wound open after a soaking, with gloved hands (to protect yourself from sepsis), give the opened wound a firm squeeze to get the pus out of the pocket. Poultry pus is thick and cheesy, unlike watery human pus. Once you've got all the goop out, fill the wound with triple antibiotic ointment and fashion a duck bootie with 'sports' tape (sticks to itself wonderfully, but won't stick to or damage her skin), do not make the bootie so tight that it cuts off her blood circulation. Change the dressing every two or three days, examining the wound for continued infection or inflammation.
