No way, dont listen to your neighbour is he a qualified vet? Its never too late for a dog to lose weight, dont just take my word for this because Im not 100% sure or the ins and out of it but have you tried swimming sessions with your lab? I've heard them can lose weight in a healthy way from that, maybe talk to your vet about seeing if you can change her food to a lower fat food, but if my neighbour said that then they would be on the recieving end of some quite rude names.

Think about it, what someone gets old is it best to let them die out of being fat and having a heart attack or try and keep their weight down and keep them fit?

How many treats does she get? maybe ask your vet for low fat treats like carrots and apples etc. some fruit and veg cannot be given to dogs so research before you give her anything