M.G.
Don't let your mother give her any food is my main suggestion! Children's stomachs are not ready to digest at that age. Even the baby food companies chart starting with single grain cereal around 9 months of age, usuallly rice is the first food to teach the stomach to digest, then oatmeal, then on to the veggies then fruits.
peas, green beans and sweet potatoes should be the first veggies, sticking with one food for three days to see if there are any reactions, then go to the next, and so on. You want to introduce veggies first, then fruits, so that your daughter will like the taste of veggies first.
As for the lactose situation, was the vomit projectile? if so, then she may have an allergy. You can try the enfamil lipil ar which is "added rice" protein. It helps the formula stick better. You may have to try different formulas to find out if it is just one better than the other for her. I was on a soy based as an infant, but my favorite drink today is milk with no problems, so don't stress! M. G, Hemphill, TX