When is the last time she laid an egg?
It does sound like stridor, but I would also make sure her crop is emptying overnight.
I have a 7 year old hen that lays every once in a while, but she is starting to show some signs of reproductive problems with a bit of fluid in the abdomen and her crop is slow to empty at times. When she's having a little difficulty, she makes a sound similar to your hen. I have yet to drain her since the symptoms come and go, but do check to see that her crop empties, if it doesn't then I address that following this article
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/