Reply #1: my wife, haele

[lazarus]

says it was a series of short stories, if she recalls correctly. The cat was named S'Kittie or something like that, and the cats were bred to work with pilots or navigators.

She's going to look further.

Edit: On further research, she found a book called Catalyst, by Anne McCaffrey and Elizabeth Ann Scarborough.

The group of short stories is from an anthology called Cat Fantastic. They were written by Mercedes Lackey. She's fairly sure that's what you're thinking of, as they involved giant rats, too. And diplomacy!