Could be a allergy to casein (the milk protei). Let me just tell you this, I had a problem with my stomach a few months back and I gave up dairy for like 1 or 2 months and tried to get back on dairy and would get constipated. In other words it got even worst when I tried dairy now. I talked to a nutrionist and she said its possible that it gets worst when you eat dairy now bc you gave up milk/dairy for a long period of time and I might of lost my enzyme and ability to digest milk. So in other words once you give it up your child may not ever be able to tolerate it again. With that being said, do some tests with her diet. Maybe its just milk bothering her, not cheese, or vice versa, etc..At worst if yall have to eliminate dairy, soy milk is great! I like the omega 3 one better then reg milk. They also got decent soy cheeses, so no worries there are tons of alternate options in todays world! Also remember that many products contain milk; like dorritos, many breads have milk stuff like whey or casein, but maybe your child will be able to digest those fine bc there's not a ton