Protectiveness over store

[ec140466]

I have a 3 year old pomeranian/sheltie cross who is a great little dog, most of the time. I just started working at a pet store about two months ago and bring her with me everyday. At first she was fine with everything but, now she has gotten quite protective of the store. People are fine, as well as little dogs, but any big dog that comes in she barks and barks (which I know is partly out of nervousness). We are currently using Cesar Millan's method of making her submissive towards the dogs, as well as giving any of her bones to the other dogs to show her that they aren't just her bones. This method is working a little bit, but I would like something more. Any suggestions would be great appreciated!!