You are so right it is stressful for them to be alone so when I keep a duck inside i bring a friend duck in too. She may have just stepped on something sharp and tore it open. Their little soft webby feet go through so much. I wonder how the webbing survives . I walk around my yard picking up anything like sticks or stones might scrape them.
Cleaning , ointment , and wrapping can be enough if she needs to stay out with her friends just change the bandage every day. I had a chicken who needed to stay out when she was healing after bumble foot I just brought out with me every morning my spray bottle of vetricyn and tube of ointment and the vet wrap, scissors, plus waterproof tape. , in a Ziploc gallon bag when I would redress her foot outside in the morning every day..
you said she is very heavy. Is she overweight? What is her diet? Perhaps too many treats?