Try goat's milk. Studies have shown that it's tolerated better than cow milk--It''s usually easier to digest. Or, try one of the other "milks" - almond, rice, coconut, soy, or.... But be sure to get the vitamin fortified version, and be aware that a lot of them have a lot of sugar in them.
If your concern is that she get enough calcium/protein/fat and that is why you're giving the cow milk, try not doing the milk but do cheese or yogurt instead & see how that goes. (There is very little if any lactose in cheese, and shouldn't be much in yogurt--the microorganisms that turn the milk into yogurt & cheese use up part or all of the lactose).
And keep in mind, if the milk/dairy does work out for you, there are lots of other good ways to get those nutrients and in lots of parts of the world, dairy is not an option or part of the food.
Edited to add: If you make changes in her food, given her history of acid reflux, go very slowly-- for example, you could try to reintroduce the cow's milk but use only a very little mixed with the formula. If she tolerates it well, leave it that way for a few days, up to a week, to let her body get used to it. Then maybe try increasing it a little bit at a time, gradually over time.