It is hard to tell with the dirt on her foot, I'm not seeing the "core" that you usually see in bumble foot. It does look infected though. If she were mine, I would start by giving the foot a good scrub and a thorough cleaning with peroxide, betadine, or chlorohexadine. I would probably even rub some neosporin on there (make sure it doesn't have pain killers in it though). Then I'd put her on what ever bedding I thought I could keep the cleanest (maybe paper towels or a towel I could wash or rubber matting). I'd also treat with antibiotics.
If during the cleaning you do see a dark plug (that would be bumble foot) and I would treat for that.
Not that I know of, although I had a friend that said one of his chickens had it and after a bad experience with the surgery, said he was just going to let it work it out by itself, and he said his chicken got better. I would opt for the surgery myself.