Every cow is different from every other cow just as every human is different from any other.
The soul within the cow s body gives a unique individuality. If you spend a little time observing the cows and oxen, you will notice this and come to realize the cows have a society of their own. In a herd there are those who are the leaders. In this case it is Vraja and Gita. They have the biggest bodies and horns, so in the bovine society they have the power.