Hi C.
Allergies vs intolerance is always an issue. Sounds like the elimination of milk is working. That is good news. No one should be vomiting nightly, chronically, without medical diagnosis. Don't eliminate reflux however, did you by any chance feed her later, closer to bedtime? Some people can't lay down for 3 hours after they eat. Just one thought.
Is it possible that she had more milk products that day than any other recent day, which put her over her tolerance level right now. It takes about 6 weeks for an allergen to get out of your system, so it is possible that as she heals she may be able to tolerate more. Perhaps you don't realize it is like filling a glass as long as you don't reach the top, the glass doesn't spill but add another tsp and it is a spill. When allergens get to the top, you are OK but another tsp and you react.
I am lactose intolerant. I took the test, don't recommend that but since I had always tolerated ie: 8 oz, I just was not sure about change in my system being just that. I now don't tolerate the amount of milk in some commercial breads.
Milk allergy is not the end of the world. In fact, with our oldest, the allergist said I was poisoning him by giving it to him. That made me realize that although milk is good for most people it was not for him.
By the all my children are allergic to milk.
God bless you and give you wisdom
K. SAHM married 38 years--- adult children -- 37, coach; 33, lawyer, married with 7 mo.; and twins 18, in college, journalism,GPA 3.9; fine arts, GPA 3.7-- by the way-- we home schooled.