We stopped recommending OPC for dogs because too many dogs got extremely ill. They didn't die, but had to go to the animal hospital for fluids. So, it's too risky, and you don't need your Lab going through that with everything she's dealing with.
One thing I would recommend is colloidal silver and colloidal gold in her water. An ounce of each every day. This should help in case she has some sort of a virus and it should also help the pain in her neck. Keep in mind, I'm not a vet and I have no idea why she is so cold.
You can get the best quality colloidal silver and colloidal gold at Utopia Silver. This is the only silver and gold I use for myself and my pets and I've had excellent results.
Additionally, I am going to give you an article for hip dysplasia in dogs but the supplements in this article should also help with your Lab's neck.
I don't know what the cold is all about. What did the vet say her temperature was? Prayers are with you.