in my opinion, and i am by no means a vet, this looks like a rather nasty bite that has been infected with fungus.
if it were me, i would take the following steps. please take any and all advice i give with a grain and salt and the knowledge that i‘m merely a 17 year old kid.
1. tub her immediately, using fresh, clean, dechlorinated water
2. call a vet and set up an appointment. this is a nasty case that she could very well die from if not treated properly.
3. discuss possible amputation with the vet. the leg appears to be too far gone to recover from (in my opinion - see the first picture in the last set you posted) if necessary, i can assist in giving advice for at home amputation, (under anesthetic) but would much more recommend a vet doing so, as they are trained professionals
4. introduce IAL (indian almond leaves) to the tub or start giving tea baths
5. consider salt baths, and read about the dangers they can pose, as well as the benefits
6. change the water 100% on a daily basis