We have two frenchies. One is the calmest, most submissive and docile dog I've ever encountered (to put it in perspective, he lays with my holland lop rabbit and they're both comfortable). Our other frenchie (a female) is the dominant dog in our home and is very jealous. She gets the dog"Mohawk" if our male frenchie does something to upset her and will jump towards him, crouch over him and make a lot of noise. She never actually attacks or injures him. She is a very anxious animal. They're only a year apart in age, raised in the same home since puppies and completely different. How have you guys prepped your dog living situation when you're dealing with an aggressive dog?