u/LouWasHere2

We recently brought home Larry, a young male kitten. We already have two cats, Dixxon (male) and Cora (female, almost 2). Dixxon has adjusted pretty well, but Cora has been having a really hard time.
This isn’t just normal hissing or an occasional warning swat. Cora will actively stalk Larry, wait until he’s cornered, chase him, hiss/growl and go after him. Tonight things escalated and she also went after Dixxon. They ran under the bed and, instead of disengaging, Cora followed him and went after him again.
We’ve been trying slow introductions/separation, have 3 pheromone diffusers running, and our vet prescribed gabapentin for Cora for stressful situations. We gave her a dose tonight and separated everyone, but giving her gabapentin every day isn’t a realistic long-term solution.
Cora has always been a very independent cat. She doesn’t like being held and only tolerates petting when she wants it, but we’ve had her since she was about 3 months old and really don’t want to rehome her. At the same time, we can’t allow Larry or Dixxon to get hurt or live scared in their own home.
Has anyone dealt with this level of inter-cat aggression and actually gotten everyone to coexist peacefully? Did you completely restart introductions? Use a veterinary behaviorist or long-term anxiety medication? How long did it take?
I’m especially interested in hearing from anyone who had a cat that was actively stalking/chasing the other cats, rather than just hissing during an introduction. I’m trying to figure out what our realistic options are before even considering rehoming Cora.