Hi
We started our DS on cows milk around the year mark too. We broke it in gently, giving his morning bottle as cows milk (so we could keep an eye on how it effected him during the day), for the first week and formula for his other two bottles (afternoon and before bed). We changed his afternoon bottle to cows in the second week until he was full cows milk by the third week.
As you will imagine, just watch for any signs that it's giving her a sore tummy and introduce it as slowly as you feel comfortable. Sorry if TMI but we found that his poos were "loose" at first which was just his tummy adjusting but they soon adjusted back. If you're nervous perhaps try some yoghurt's first if you haven't already?
Good luck
