So over the past week I’ve been slowly introducing a new cat with my 4 others, day one was no contact between them just some sent swapping on toys and we moved the food dish closer to the room the new cat is in everything went very well. The next 2 days we slowing started letting them see each-other through a gate with the exception of my one female as we knew she would need more time and everything was going very well. For some context my female cat hates my partners mother passionately and one of her cats had a hormone issue recently that caused a fight between the two so for the past 2 maybe 3 months my female has chosen to stay in me and my partners bedroom unless she needs to eat or use the bathroom. All the other cats still see her and she does good with all of them now even the one she had a fight with as of recently and she almost didn’t react last time a cat was brought in the house. So the next day after introducing the new cat to the rest of them we let her see him through a gate and she looked at him but didn’t seem to mind so the next day we let him in the room.

After he came in the room she seemed a little more alert but not showing many signs of stress, no puffed tail, ears were normal, and she was laying down calmly on her cat tower. But once the new cat got about 3 feet from her, her whole attitude changed. She hissed and swatted at him which is at least to me normal behavior for a first meeting with no barrier. She still didn’t seem really stressed still none of the signs I listed she just seemed mad? If that makes sense? I went to go pet her about 15 minutes after and she swatted at me lightly but you could tell it wasn’t playful and now she’s been very distant from me.

So I guess what I’m asking for is any advice and help as to why this may be happening or what I should and could be doing better? I don’t want my female to feel like this is not her home anymore that would truly break my heart.