You really don't need cow's milk at all. It's mucus forming and constipating for many people. If your little one has that problem now, she will more than likely have that problem if you switch to cow's milk. I use a variety of milks in our house. We have 4 children and they drink almond milk and soy milk. I only have one that uses cow's milk because he wants milk and doesn't like the other milk. You can get good fat from so many other sources. As far as calcium, same thing. I actually have to give my one child that drinks cow's milk, a calcium supplement...ironic huh. Not to me.
When I nursed my little ones, I had to stay away from cow dairy because they would have problems with it. There are many people whose children have problems with cow's milk but don't know it. You already know the signs with this sweet little one that you have. Good luck!