If her crop is filling with air, there are air producing organisms in there. Search for discussions on 'sour crop'. Sour crop can be due to eating something spoiled/gross. Chickens like to do this.
This may be her only problem or it may be secondary to an underlying problem. If material is passing from her crop to the vent (pooping), she probably does not have a crop impaction- but there certainly sounds like she has an overgrowth of something in her crop. Bacteria and yeast can produce gas. Home treatment can be acidifying her crop to try to kill things in there- ACV is an old remedy. Getting her to eat/drink more to flush out the crop is good (dilution and passage of the bad bugs). A vet would likely empty, wash & flush, then fill the crop with good/fresh food. Lavage & gavage.....
This may be her only problem or it may be secondary to an underlying problem. If material is passing from her crop to the vent (pooping), she probably does not have a crop impaction- but there certainly sounds like she has an overgrowth of something in her crop. Bacteria and yeast can produce gas. Home treatment can be acidifying her crop to try to kill things in there- ACV is an old remedy. Getting her to eat/drink more to flush out the crop is good (dilution and passage of the bad bugs). A vet would likely empty, wash & flush, then fill the crop with good/fresh food. Lavage & gavage.....