Oh my gosh! She is a beautiful kitten. She's gonna be stunning when she is all better. I assume they gave her a dewormer while at the vet? That could be why she is so weak since the vet visit. It'll probably take her a few days (after the dewormer) to start feeling better. About that time she should be doing better with the URI. If she is doing better since you got her (and feeding well now) AND she is now being treatment for all the crummy stuff in her system, then she should be able to walk away 100% healthy. Is her eye gunk related to the URI?