My shepherd is two and has always been a very friendly dog with people and dogs. We very seldom have her on a leash because we live ina very country area and she minds well. Well today i went to load her up in the truckmso we can go walk through the woods and a neighbor was walking his dog.( A male mix shepherd) BELLA wasted no time in making sure he knew she was there she went up to him with all her hair spiked and smelled him then he/ she started to go at it. Nothing serious but enough for concern for me since shes never done it. I called her back and she came but she has never done that. Then again today another neighbor was walking there small jackrussell and she opened my front door gate and ran after the dog i didnt see what happend i could only hear all the barking i ran after her and she came back right away and went and layed down in her kennel. I dont know why she would start acting like this now? My only guess with the dogs is they always walk by our fence and she hates it but she has never lunged at other dogs. In a training class she submitted to a chihuahua so why now? any advice?