@Birdsnstuff (Not a doctor, so no professional medical advice included)

Might be a long shot but could be worth having them check if it's GERD. If she tries sleeping semi-elevated (35-45 degree angle) and the symptoms go away, then it's definitely worth checking. The feeling like she can't breathe might be apnea related which the sleep study should help identify. G'luck, and hope she feels better soon!