from what she describing it sounds like motility problem: crazy air burping, food not going down and building up in the esophagus, nausea and very strong gag reflex. but she is very reluctant to do gastric emptying study - she cannot even look at eggs.
but still even with nausea she is eating around 1800 - 2000cal a day and loosing weight without any BM issues. just cannot figure it out
From Dr. Google
Signs and symptoms of SIBO often include:
Loss of appetite.
An uncomfortable feeling of fullness after eating.
Unintentional weight loss.