So sorry to hear of your problems with this collie, goosepimple.
I had a rescue BC-cross who nipped some people some of the time. I sought advice.
Here is the advice and what happened.
I asked John Cree, he of Police Dog / Working Trial training fame, and he was incredibly generous with his time and thought. From asking a lot of questions, John established that it was nervous aggression and not a generally nasty dog. (From your description I can't determine which it is in your girl's case; ours never ever looked even close to nipping us.)
John gave us suggestions for making a safe haven for the dog to which it could always retreat and basically hide, and could be certain that no-one would ever come to it there or make it feel nervous there. I've talked about this before on another thread here.
He also advised that we should not be with the dog the whole time, so that he was a bit more self-reliant and less dependent on us and our presence.
It all did make a big difference, and the dog stayed.
Prior to this, an experienced dog handler in our village had given us the benefit of her experience, saying that she had had a similar situation years earlier, had done everything she could, but in the end the dog still nipped and she had had to have it put down. She'd tried for so long that it really broke her up having to give up on it. She was hoping that by telling us her story she would save us some of the same pain.
Sadly, over time, the dog did begin to leave his safe areas and sneak up behind people who were not in any way threatening him - or even on his territory - and nip. So we did have to have him put down. At that time, that was the hardest decision I had ever had to make. A vet friend of mine had told me years earlier that collies congenitally nipped, they were bred that way to nip the sheep on the backs of the legs to chivvy them along - and that the most common serious wounding caused by nipping collies was not, as you might imagine, missing noses or scarred faces - but damage to the penis and testicles of little boys, up to and including castration. Remembering that strengthened me for the one-way trip to the vet - no way could I face that kind of harm being caused by a dog of mine.
These days, nippy collies are a lot more rare, most breeders of pet or working stock will not breed from a collie that shows any aggression towards a human and the traits have been, if not eradicated then at least massively reduced.
Having been there myself, I think it is a very personal decision so I would not presume to tell anyone else what they must or must not do. But for myself, I certainly would not take any risks with a nippy collie near children; if I had to have the dog then it would be in a secure pen when there were children about.
Subsequent to the above story, having a different problem with a later rescue dog, I bought John Cree's 'Your Problem Dog' book, which was full of insight and great practical suggestions - and in this case, I am pleased to report we had complete success and the dog died peacefully of old age at home five years ago.
Whatever you decide, goosepimple, I wish you the very best of luck - and if a private conversation would be of any help, drop me a PM.
Best,
Sally x
