Newborn lactose intolerant?

Patient: My granddaughter is 2 and a half months old. She was born at 35-36 wks and weighed 4 lbs. at birth. She has been fed a combo of neosure and breast milk. Over the last two wks she has become increasingly fussy, spitty, and seems like she is in pain after eating. Her pediatrician has tried her on simethicone, zantac, and currently has her on prevacid and carafate.She lost a few ounces,so she is going in for weight checks. (she did double her birthweight by 2 mos). Is it possible that she may be lactose intolerant?