Hi, I am new to this site. I am looking for some advice. I adopted an ACD mix from the shelter when she was around 2 months old. She is now 3. She has a lot of energy as expected from a cattle dog mix. I believe that she is mixed with either a hound or some sort of shepherd. Her name is Codi. The other night I rescued another Australian cattle dog mix (also female). She is 9 months old and mixed with a Australian Shepherd and a springer spaniel. Her name is Ray Ray. I brought them home and had them meet at the park by my house in a hockey rink where I could let them roam but still had the leash attached to them incase there was a fight. When I got them to the hockey court they were getting along fine but then the new dog got scared and ran away into the corner. The next morning things were good. I had taken them on a long walk together and they started playing. The only issue was when someone walked into the door my old dog would get mad If the new dog tried to greet that person first. Now they have started to play inside the house. But sometimes if the new dog does something my old dog doesnt like she will show her teeth and then nip at the new dog and the new dog will back away. My question is this behavior normal? Will it eventually stop? Is this a bad mix of dogs?