It’s possible that Yuca simply doesn’t enjoy puppies. And that’s NORMAL and perfectly okay! Puppies are annoying. Your best bet is to put a LOT of attention on working Coco’s brain more. A tired puppy is a good puppy, and the BEST way is to work their brain. This would be obedience training, beyond basic sit/stay/down. I know group classes aren’t really a “thing” right now, but I’d look into classes through Denise Fenzi’s dog sport academy: https://www.fenzidogsportsacademy.com/
Maybe work Yuca while you’re at it. It’s a good way to keep her engaged, and working them together can help.
Hi there. I’m sorry it took us a while to respond…I’ve been pondering over this since you initially posted. I think you may have to consider permanent separation. This is doable in a cat household, as you’ve seen, though it can be annoying, but it might be safest for the clowder.
I assume you’ve tried Feliway?