Answer:
It may be that your child had a viral intestinal infection that has left her temporarily
lactose intolerant.
If she is otherwise growing well and has no abdominal pain, flatulence, or diarrhea when on a diet excluding only lactose then it's quite unlikely that something else is going on.
It may or may not help but will certainly not harm her to try adding a probiotic to her diet for a month or two and then trying lactose-containing foods again. Start with a small amount of lactose.
Check with your pediatrician if she continues to have these episodes of gastrointestinal distress.
If she is otherwise growing well and has no abdominal pain, flatulence, or diarrhea when on a diet excluding only lactose then it's quite unlikely that something else is going on.
It may or may not help but will certainly not harm her to try adding a probiotic to her diet for a month or two and then trying lactose-containing foods again. Start with a small amount of lactose.
Check with your pediatrician if she continues to have these episodes of gastrointestinal distress.