I have two indoor cats, both altered and separated by six months. The boy cat push through a window screen and got out last night. It wasn't for long and I only noticed when I heard him howling to get back in. The girl cat was on the inside of the house and was batting at him, keeping him from getting back inside. Well I moved her and he got back in but she has been treating him like a "stranger" ever since. They usually get along perfectly but now she follow, growls and hisses at him. He is just trying to do his thing but they have gotten into some loud scuffles. She also growls and hisses at us when we try to interfere with her "work", What's happening?