Thanks ladies. <3 She was not my kitten, but I met her and she was just sweet as can be. One of her nicknames was "glitch" because often she'd do something, like burying her poo in the litterbox, and get "stuck" doing it continuously. Sometimes she seemed to not have all her screws, but neurological dysfunction can be a symptom of dry FIP, which at this point they're quite sure she had.
Her simple mind just added to her sweetness, though. She was happiest when in a lap, being loved on. She was a very simple, sweet kitten. I am sad I will not see her again. Next I visit I'll spend a little time at her grave - she is buried under a tree in their yard, with a big heavy flat rock atop her grave that my sister will decorate as a pretty gravestone in the spring.