That's what I would do.I think so too, no vet available to me unfortunately I have searched for one. I could attempt an amputation, I've seen them done, but I wonder if it's more humane to euthanize.
Do you know of an antibiotic that would help her? I've only used Tylan 50 before but my understanding is that is for respiratory infections.
I'm going to the feed store today to get an antibiotic and planning to do whatever I need to do tomorrow.