I really do feel for your loss....did the exact same thing one week ago today...for same reason. My lovely 5 year old BCM hen, Mary, had a case of bumblefoot that I was working on, then realized she also had gotten frostibit during one of the infamous Polar Vortexes that hit us hard. I realized later, to my chagrin, it was my fault indirectly, that she got frostbite. I think when the waterer leaked out, she must have stepped in the resulting puddle and with her feathery feet-- that's all it took. I tried to solve the waterer problem, obviously not soon enough. Just didn't realize this could happen, the extreme winter was hard on my birds.
Anyways. tried salve, keeping it clean and dry, wrapped...after 2 months she was losing weight and sadly hobbling around with a black foot and swollen leg, plus black toes on the other foot. She was in pain and slowly distancing herself from the rest of the ladies. Thanks goodness for my husband and a good friend--they did the deed while I cried in the house.
I'm not a very good pioneer woman.