Hugs, its is really hard at first. As Lizzie said, there are varying degrees of intolerance but they all grow out if it!
There are only so many mistakes you can make with the diet, once they are all made, you will be set. So many of us have made every mistake, that's the only way we can learn, I guess!
Give yourself 4 weeks to get on a roll, just start fresh each day after a slip up. it really does take at least 3 weeks.
My DS1 had reflux and MSPI, he grew out of reflux at 9 months, and also the intolerances. When I weaned him off his meds, it showed his relfux was gone, so I slowly introduced dairy into his solids from least reactive to most reactive. By 1 year old, the only dairy he hadn't had was cows milk, I waited till 18 months for that one. Let the meds weaning be your guide as to when you can introduce dairy, but most recommend not to give any till 9 months if they had a history of MPI.
As you know my DS2 has multiple intolerances,
Let her symptoms be your barometer. Is is easiest to start with complete elimination so you have a baseline of staibility, and gradually instroduce dairy from there. You will find what she can and can't tolerate easily because you will be comaring her reaction to her baseline of "wellness". If you are finding complete elimination too hard them eliminate what you can, and *hope* that you get some form of stability. If you feel that she should be better, then eliminate more and more until you get your settled, painfee bub.
As you know my DS2 has multiple intolerances, after eliminating dairy, soy, gluten and gassy foods, and low additivies, I still felt he was reacting to foods and could be happier and more settled. It was obvious that foods were still causing him issues with his poos and relfux. Hence I started an elimination diet. You just got to go with your instinct and trust that you know your baby best.