My family currently owns a six-year-old female Shepherd. We adopted her when she was a puppy as a second dog to our older yellow lab. She's always been very well behaved, and she is not at all vicious.
However, she always had to be Number One dog. Quite often if I was paying attention to our Lab, our Shepherd would push between us, things like that.
We lost our Lab earlier this year, and have just started looking for a second dog. We went around to shelters and found a gorgeous bull terrier mix that was clever and very well behaved (plus good with cats, a trait our shepherd... uh, does not have). Today we took our Shepherd up there for a meeting to see how they'd get along, figuring it would be fine because, as I said, she is never vicious or aggressive.
The other dog was happy enough to meet her, was trying to initiate play, but our dog was... not happy with it. She never snapped or anything, although they did get a little physical at one stage, but she kept putting herself between us and the new dog - even with the shelter worker. Towards the end of our meeting she was standing about ten feet in front of us, keeping the other dog away.
The shelter worker wasn't happy with this and didn't feel right letting us take her, which I can understand, but I was wondering if this... possessiveness of people was normal for Shepherds, and if it fades over time or if there's something specific that can be done to calm her down a little? We would really like to get another dog, but we can't be constantly worried that our #1 will keep this act up.