I'm sorry about all you are going through with the puppy. A good breeder will give advice for the life of the pup and will accept a puppy back at any time. If you decide to relinquish the pup, then by all means - contact your breeder first. ( It may even be a contractual obligation on your part.)
There is no way on earth I would return the pup to the breeder. In fact I'd be reporting her and the condition of her animals!
You would be in violation of contract and could be sued. That would have been your decision.