I was like that when I was young and I gave up also. Looking back now, I know I didn't drink enough water. Have her check and see if she takes water bottles with her everywhere, or drinks water all day.
She probably has a bad case of candida and a poor diet. Show her the symptoms of candida and see if it fits. She needs to take it seriously. Ask her where she thinks all the food goes?
From another poster I heard the fecal mater stays in our intestines and gets covered over with lining and provides a wonderful place for parasites, yeast, bacteria and toxins that eventually cause arthritis, MS, acne, psoriasis, and on and on!!!