She might have drug resistant diarrhoea or this may be due to intolerance to certain food products like milk, milk products or wheat products . Stool RE should be done to ascertain the cause - whether this is bacterial or amoebic diarrhoea or there are features of indigestion.
Next Steps
You may consult me online at Practo.
Health Tips
She should take regular diet and avoid fatty, spicy meals.