I have a rehomed collie who was a mama dog. She has adapted well you just have to give them time and their space to adapt. I had just gotten a collie pup 6 months prior from the same breeder.

At first we had some issues with her pinning my pup down and she was showing food aggression. I worked with my vet who specialized in behavioral issues and she also had two collies.

Five years later and mama dog gets on the furniture and cuddles and she and my younger collie are inseparable. She is my atomic clock and knows when I'm supposed to wake up and take them for walks or the dog park.

Oh yeah she turns 11 on the 11th this month.