How long can I continue to dehydrate my daughter and how long will it take her to finally drink the cows milk?

Try a slower weening process. Try mixing 6oz of milk with 2oz of regular milk. Then each week switch ounce for ounce. That's how I weened my son. If she won't drink milk replace her need for calcium with foods rich in it. Yogurt, cheese, and some leafy veggies have calcium and certain juices do too. This way in your switch she is getting what she needs.