Diet/Nutrition

My Mom is stage iv pc with mets to the liver - her CA19.9 is 109,000.  She is 66 and was diagnosed 7 months ago.  She complains that nothing tastes good anymore, but when she does eat, she gets nausa and/or diahrea.  She's tried eatring smaller, healthier meals, but even when she thinks she is eating right, the side effects still come.  Any suggestions?