But HV, surely some foods that cause sensitivity to Mom get passed as sensitvity to baby as well...?
Certain things have been shown to pass through breast milk such as garlic and strawberries. So this could be the problem as well.
I was actually allergic to mother's milk, but this does not seem to be the case here since she seems to be comforted by the breastfeeding. And since you would not eat the same food all the time the lack of flora makes more sense. The symptoms are also fitting.