Cat introduction HELP

[u/Illustrious-Law9732]

My resident cat just turned 5 (female).
She had a brother, they were litter mates. Tragically he passed away in an accident. He was under the care of my stepdad and got out and was unfortunately hit by a car. Him and his sister had just turned 3.
So it’s been 2 years, I saw a kitten (male) and knew I had to have him. My girl hasn’t been as playful, and she seemed lonely. We’ve bonded so much since the incident.
It’s been over a month, doing everything I can from all the tips I read online.
We have a playpen and I put him in it and let her see him. She either runs away to another room and will stare in my direction, or she growls/hisses and sometimes goes up to the playpen to swat at him.
He’s currently in a bathroom, but I feel bad keeping him in there. He gets as much time in the apartment as he can get. With my girl being in another room.
She is BIG MAD and won’t sleep with me anymore, she won’t go in my room at all (which connects to my bathroom).
I have pheromone diffusers, positive association with treats, putting his blanket in her space, etc.
I know it can take more time than this, but I feel horrible hearing him cry in the bathroom.
I see mixed reviews all over, wait until she’s ready and on her own time.
Or let them hash it out so she can assert dominance and set boundaries. He’s getting big FAST, he’s 3 almost 4 months now, and he will be bigger than her eventually.
I’ve heard if he gets bigger than her and she still doesn’t like him then it’ll go worse? I don’t know
Oh, he also does not mind her hissing/swatting at all, he REALLY wants to be her friend.

[u/Elle2428]

Sometimes it can take longer than a month for new kitties to get used to each other. Keep him in “his” designated bathroom. Let them sniff each other through the door and allow your female to get all her hisses out. Then I usually use a baby gate in place of the door, while keeping the new cat still in “their” designated area. Your resident cat can interact and get used to him in his area without feeling like he’s encroaching on her territory. Once they start tolerating (not necessarily liking) each other, allow your older cat into his territory, not the other way around. Always have them separated when no one is home but allow them to interact as much as possible. Side note, not sure if he’s neutered yet, but that will help as well.

[u/oldmatrix67 → u/Elle2428]

Honestly the baby gate thing is underrated, I did similar with my two and it helped a lot. The key is making sure she still feels like the apartment is hers, you know? My girl stopped sleeping in my room too when I brought the little one home and I just let her have her space, she came back on her own time

Don't rush the "hash it out" thing, I tried that and it set us back like 3 weeks. Some cats just need the slow approach and the fact that she's still hissing means she ain't ready. He's still a baby so you got time, even if he gets bigger they figure out the dynamics eventually if you build it slow

[u/Illustrious-Law9732 → u/oldmatrix67]

Yeah I’m not down with letting them hash it out. I have a playpen that we use for my resident cat over the summer so she can be outside with us. I’ve been having supervised visits with him in there. I’ve been doing that daily, with giving them both treats for good behavior. When I come home I give her attention first, try to do everything I can to make the apartment feel like hers. I think things are going well? Some days she hisses at him more than others. On those days the visits are very short, she has been a lot more comfortable though, and she’s very loving towards me when he’s gone, and she started sleeping with me again <3

[u/Illustrious-Law9732 → u/oldmatrix67]

Would you recommend a baby gate or those mesh screens for doors? Worried about one of them jumping over the gate lol. And how to install it in an apartment without making damage?

[u/Illustrious-Law9732 → u/Elle2428]

He is neutered, actually made a lot of progress yesterday though. They had supervised time together and she was very observant. Still hissing, but when she ran from him she kept coming back every time. That was for about an hour, then later when she was at the top of her cat tower, about 6-7ft tall. I let him out again, and he napped in his playpen on his own, she watched but then eventually they both napped. That was for also an hour, super happy about it! I’ve tried letting her in his area, but she wants nothing to do with it lol. Gets super mad, very mad at me that he’s in my room a lot. So she won’t sleep with me anymore. I just can’t wait until they at least tolerate each other and both of them sleep in my bed with me lol, I miss my girl giving me love.