Update. This morning we went to vet. She told us that it looks much worse on pictures, at the moment this is definitively not for amputation. She told us that it's necroses but in fairly early stage. With vet we had a better look at the affected tissue, actually there is no black tissue, only light gray. Picture with flash shows correct condition, other one without flash is too dark. Vet also told us that this is far from terminal stage and that we got plenty of time to observe her condition before we proceed with amputation. Also area affected with necroses didn't form yet so it's unclear how much of tissue would be needed to remove.

Today she started treatment with antibiotics and will continue to do so for next ten days. In that time situation should be much clearer. Our vet feels that antibiotic treatment at this stage should give very good results. If it does not it will help to show how much tissue cannot be saved. And snake will be much better prepared for operation.

Once again thank you for all your advice's and support.