I’m at a loss here. My partner has been moving into my home for the past few months, and he brought his cat. We first placed her into her own room so that she could settle in, and swapped rooms between her and my two cats at least once a day.

She seemed comfortable, so while using a toy and treats, we tried having her in the same space as one of my cats. They seemed fine at first, but she was startled and jumped. They immediately attacked one another.

We isolated her again and started all over. I added a pheromone diffuser, which seemed to help calm her. But I did notice that the cats were now occasionally batting at one another under the door. So, I put something under the door to prevent this. But they would still gather at the door, crying.

I bought a catio for her, thinking that she could get used to the sights and sounds of my cats while in a safe and protective environment. Nope. They immediately lunged at one another as soon as they could see each other.

I feel like it’s pretty hopeless at this point, and I have screwed up the entire process somehow, but I also don’t recall it being this hard to introduce cats before.

Thoughts, advice?