zero fat is HIGHLY dangerous. Change the fats to strictly olive oil, coconut oil, clarified butter or red palm oil.
There are four VITAL vitamins to the body that are ONLY carried by fats: pottassium (K) A, E, and D. Any one of which affects important body functions.
Change the diet to foods that increase bile flow (lemonade from REAL lemon juice and HONEY ONLY, NO SUGAR) beets, etc. Start researching liver healthy foods. All those dandelion "weeds" out there aren't weeds at ALL, but IMPORTANT nutrition for the liver. research and learn how to pick the leaves and dry the roots. She'll be IMMENSELY better just from the lemonade. My son and I have had the fat digestion problems for years, and I actually decided NOT to post the study showing that we pass this on neonatally. Stay AWAY from ALL OTHER FORMS of oils. The vegetable oils are VERY hard on a liver that is already taxed. So that means no fast-food restaurants either. No fried foods, period, unless at home and with the oils listed above.
Don't give up. The stones don't actually pass from the gallbladder but can be slowly dissolved (this is even acknowledged in the medical communty) and broken down and eventually passed that way. Sometimes an actual stone will pass a duct, but this is actually rare, as they usually block the duct and cause jaundice and other medical problems. I'm not a doctor, and balance all that you hear or read with your own logic, your own experience and other expert advice (yes, your doctor.)