Thanks for contacting us. If it’s actually the Pre/Post shake that’s causing the problem she may have difficulty digesting a milk protein but that’s unusual since there is virtually no lactose in the dotFIT products. What’s not uncommon is to experience an upset stomach from drinking any liquid meal too fast such as a protein shake. Sometimes when people first start using a protein shake, they drink it fast and that sudden amount of food reaching the gastrointestinal tract so quickly can cause an upset stomach for sensitive people. You might have your client try drinking it over a 10-15min period and as the body gets used to it, they can drink it quicker. You could also try our vegan protein since there is no dairy in the product. It’s called BestPlantProtein.