s job is to manage blood flow to the gut. Vomiting, bearing down to have a
bowel movement, or conditions that drop blood pressure amplify the effects of the vagus nerve and redirects much blood to the gut which may lead to fainting.
Dehydration, psychological triggers such as anxiety, panic disorder and stress, shock, drugs or alcohol, and heart arrythmia are other likely causes. It would be best to have a further evaluation done by your mother's doctor to rule out other causes.