I'm not familiar with your area at all, but is there a chance you could rehome Ally through the local vet. Or could your vet be of any help with techniques to discourage the behaviour? It must be so hard on you to go through this and try to make the best decision for everyone.

Have you tried any of the bach remedies.....is it a stress issue? I don't remember your previous posts on why or when Ally bites. Here's a good article regarding biting with some suggestions.

Cat Biting and Scratching