You will probably find that the more solid foods she eats, the more gradually they are digested and the longer she will stay satisfied, not waking up at night. At 15 months, she is more than capable of going all night without food - she will make up for it during the day.
There is no magic to cow's milk - you can try many other products for protein and calcium. I made French toast with a good soy milk and really soak the bread - I use Nature's Promise Flax & Grain (Stop & Shop) and it's pretty "holey" so it soaks up the soy/egg batter. You can try humus and calcium-fortified juices, make soy flour pancakes, and so on. For the breakfast foods, I just make up a batch and freeze them between layers of wax paper - I pop out what I need and reheat in the toaster oven. It's just as easy as the prepared frozen foods, and much more nourishing.
As others have suggested, she may have a sensitivity to dairy products - it's often called an allergy but in thousands of cases it isn't a true allergy, just an inability to digest the food because of an imbalance in the body. My son was lactose intolerant for years (hence all the soy) but after we switched him to a particular nutritional supplement, he is no longer lactose intolerant - lots of cheese and ice cream in this boy's diet now, with no problems! There is a kid version and an adult version of the supplement - they have US government patents so you know they are safe, and they are used for infants up thru elderly people, even by pregnant women. They have all the right blends of nutrients so you are getting everything you need at the same time as everything else you need! That's key. My son has not been sick since - not a cold, not a missed day of school, not one antibiotic...And he can eat everything. It was great for me to stop worrying about whether he was getting the nutrients he needed, and he really has blossomed! And now he doesn't refuse the things your daughter is refusing. Just another way to go.