She was fearfull in many ways but most people couldn't see it when they are on the other side of the door or window and she is trying to get them very convicingly and would bite just didn't have enough confidance for a real fight almost well balenced. She did have some mild fear periods when she was young reacting to cars, shyness with people even pidling. She was a bully as a pup to other dogs she owned my friends 2 bigger Rottwiler pups growling and spasing on them taking there toys & food while she could walk under them at 12 weeks they were 5 months fullgrown she would growl at dogs sometimes but just wanted them out of her face all signs of insecurity she later got over. With People she had a standoffish approch but was freindly even sucky once she got to know you but don't try and hug her or reach to fast or be to loud she would bite out of insecurity. A cowering, hiding dog, which is clear fearful behavior, should not be taught to bite. They should not be forced to bite in defence but tug training and prey bites could give the dog social confidance even with the decoy who could play with them carefully after they have had good training & leadership can come out of there shell and become safe social dogs. With fearfull dogs I'd socialize from a safe distance staying in an area as long as it took to calm the dog down ignoring them completly they will realize they have nothing to fear do it in baby steps the next time you bring them a little closer but never take them away or give attention for fear, only for calm behaver it may take some time but the results can be great. The stay in public is one of the best tools condition them to do it anywhere it can help with confidence if done often in public.