Be careful rubbing her chest if you accidentally squeeze her crop. Her crop in her upper to mid right chest has food and water in it during the day, and should empty overnight. Feel of it in early morning to see if it is functioning. Sometimes they can have rattling due to crop contents coming back up into the throat. Does she gag or adjust her crop as something is stuck in her throat? She is quite old and they can have a chronic respiratory disease, or suffer from reproductive or crop problems that slow the crop from emptying. It sounds like you have been using Vet Rx, which is similar to Vicks. Let us know what her crop feels like. Also let us know if she has any mucus from her nostrils or beak, sneezing, or watery/bubbly eye. Those are signs of a respiratory disease.