Thank you
I talked with the vet about it and she wants us to keep watching out for that kind of behaviour. She still didn't have deep pain, so we're not really sure. But if it does happen again we need to put an e-collar or at least wrap a towel around her neck to discourage her from biting her back paws. The mailing list I'm on said it could very well be neuropathy which means there are some errant messages firing from the nerves and it can be VERY painful. And with lack of deep pain, some dogs have bitten their feet so far as to mangle or bite them right off... they can't feel it.
But I want to stay positive and hope that it's something good starting.