How traumatic for you! I'm sorry for your loss and for the trauma.
The good news is that birds tend to be very resilient regarding trauma--it's a survival thing--life in the wild is brutish and short and they wouldn't last long if they couldn't overcome trauma pretty quickly.
I raise ducks, not chickens, so I can't help you with the practical concerns, but I suspect that having a buddy and some quiet and peace will go a long way.
Also, I don't have indoor pets so I don't have to worry about it any more, but when I had a cat and also kept pet mice, I had a large rubbermaid tub with a locking lid for their home. I had removed the central portion of the lid and replaced it with 1/4" hardware mesh (hot glued down). After the mice all passed on and I was raising ducks, I used that same container for a brooder and it was great. The cat would sit on top of it and watch the babies, lol, but he couldn't get in to them and they didn't seem to mind the audience.
Now I use open-topped brooders because, like I said, I don't have that worry. But if you can get your hands on hardware mesh, it's a quick and inexpensive way to make a kitty-proof enclosure.
So sorry for your loss, and I hope the chickie recovers quickly.