When I have been asked by others "what should I do?". I reply with " there is no right or wrong answer. Just make the decision that is best for the pet and try to keep your emotions out of it."
I prefer a vet who will tell me like it is. Same with my doctor. A common practice is to stay positive about treatments in an effort to maintain the patient's hope. Then once the patient says "I'm through", the doctor admits the treatment isn't working. While I understand that, I have informed both my doctor and my vet to not do that. If the treatment is not likely to work or isn't working tell me. Give me the right to make a decision based on the facts not on wishful thinking.