This kind of thing has happened many times to my ancient kitty. Your friend may very well go through a bad patch and reemerge better than ever. My vets have issued my cat a death watch more times than I can count - and with the same problems as yours. She’s still around biting and scratching.
Hang in there!
Thank you dear. I missed your wonderful reassuring post. I’m glad to have seen it. Great news to follow!