The mother was given incorrect information. Babies are never allergic to their mother’s milk. Her baby was likely allergic to something in her diet. It’s unfortunate her doctor was not knowledgeable about lactation, but it’s terribly common. (I used to teach breastfeeding classes, helped produce continuing education credit classes for medical professionals and did a lot of breastfeeding help. I owned all the textbooks and kept up on all the journal articles. It’s frustrating to me that decades later, the knowledge among “experts” is still so sketchy.)