There is strong evidence to suggest many food allergies are psychosomatic. Often, exposing children to certain foods will help them to not develop allergies. Of course, some people do have very real, and very severe food allergies. But statistically, legitimate food allergies are rare. True, human bodies aren't really designed to digest cow's milk, so cutting dairy isn't going to be harmful so long as the children are gettinf enough healthy fats and protein from otjer sources (contrary to popular belief, you actually get more calcium from sources like brocolli than from milk). You are absolutely correct, but short of providing her with scientific articles and talking to a physician, there isn't much you can do.

It would be a bummer if this was a dealbreaker, but at the end of the day the children have two parents with legal rights to decide how to care for them and your opinions will never matter as much as theirs (even if yours are the only sane ones). I used to work in a school with a child whose parents were Christisn Scientists who believed that only prayer could heal, and whatever happened what God's will. We weren't even allowed to give the child a bandaid. Ridiculous? Absofuckinglutely. But, at the end of the day their word (legally) trumped ours so we had to do what they said. If your girlfriend can't see reason, then maybe this speaks to a greater incompatibility woth you two (and perhaps and intellectual disparity). But, try educating her first by sending reputible articles, talking to real doctors, etc. before pulling the plug on the relationship. There is a lot of misinformation out there and it is easy to fall prey to the lies. Good luck.