Thank you all.
Thank you all.
Rattling and chorkling sounds, or lung rales, often mean a viral or bacterial infection, usually from something like Infectious Bronchitis (viral) or Mycoplasma gallisepticum (MG) which is bacterial and the major cause of Chronic Respiratory Disease, CRD, in chickens.
Those sounds can also mean obstruction of some kind, like an impacted crop, or even gape worm (not common in back yard flocks but possible).
If the chorkling is recurring, and the crop feels fine with no obstruction, likewise the throat (see gapeworm below if you see red streaks), then disease is likely.
With the weather going up and down, and no other symptoms (no runny noise, diarrhea), I vote for MG as that is often triggered by temperature fluctuations (dust and stress are other triggers) and can be nothing more than a croopy sound after the initial acute infection passes, which was often mild and undetected early in the bird's life.
A bird can be infected as a chick from a parent (through the egg), or as an adult coming into contact with other infected birds. Infection rate does not appear to be high, as one poultry house can remain fine while another is affected, but a bird becomes a permanent carrier once infected. MG is controllable and not the end of the world if you have a personal home flock; it simply means you are aware that your flock is infected and do not take them anywhere or sell chicks, birds, or fertile eggs for hatching. In other words, you keep a closed flock. Birds can come in but no birds go out other than those that naturally expire at the end of a long life.
Treatment for active bouts is a round of antibiotics such as Tylan or Dramycin-10.
For Gape Worm, another possibility, check down the throat of the bird to see any red streaks which could be the small worm. Treatment is with Fenbendazole (Safe Guard) in the United States. (Flubenvet is mentioned in the UK article, but that is not sold in the US): https://poultrykeeper.com/respiratory-problems/gapeworm/
Merk Vet manual that lists treatments for gapeworm (do a word search to take you to the appropriate paragraph): http://www.merckvetmanual.com/mvm/poultry/helminthiasis/overview_of_helminthiasis_in_poultry.html
I'll link some other good reading on respiratory infections and disease for other options and symptom checkers.
Good luck with her. Keep us posted if you need follow up.