The ice cream has probably upset the lining of her tummy do try a probiotic to restore it. It's hard to find medical professionals who believe in allergies and intolerances I am lucky my gp is lactose intolerant too so he has been great. Ds saw a naturopath / chiro to help guide us through his intolerances we tried eliminating everything from my diet but he still kept losing weight, he only started gaining properly once he stopped bfing and went onto the lactose free formula at 3 months.