Do you think maybe Krissy has a cold? If you look at her nostrils, are they clear, or is there any clear mucous or crusty stuff around it? We used to have a Cockatiel (along with many other parrots), and our Tiel had a cold once... would make funny "cough" noises, but most of the time he was sneezing. Krissy is old! Ours was only 3, then my Dad told us to stop clipping his wings, and sure enough he flew out the front door.
Just keep an eye on her. If she looks like she's under the weather (sleeping more than usual, not as playful), you should take her in. Poor little Krissy. Hope she's ok.