Agressive towards others dogs that are not ours?
We have a 6 month old Great Pyrenees female named Lucy. We got her for livestock protection after losing some animals to coyotes. Today, our neighbors German Shepherd was walking the fence line on their side of the property and she took off after the German Shepherd. The neighbor caught his dog and I caught Lucy. I asked our neighbor if I could approach him while he held his dog to make an introduction. I petted the German Shepherd to show Lucy her "pack leader" (me) accepted the new dog.
However, when I let Lucy sniff the German Shepherd, she snapped. So I did an Alpha Roll and firm low NO and tried again but she snapped again! This is the first sign of aggression I have seen from her. She was raised with a corgi and Labrador so she has plenty of dog experience. She loves playing with them and is never aggressive over food or toys.
I am torn on how to approach this. She was correct in patrolling and chasing a "threat" off. That is why we got her! I want her natural instincts to kick in. But how do I teach her what is a threat and what isn't?
*The German Shepherd is poorly trained and was being aggressive towards our animals a few weeks ago. Today, the neighbors dog snapped at our Labrador after Lucy chased it through the pasture. However, regardless of another dogs actions, MY dog is to obey no matter what. Or am I holding her to to high of a standard?