I don't want to be a pessimist here, but the reality is if you have livestock, you will get deadstock.  I don't know what breed the heifer is but from what you described, if she was a Holstein she would be as good as done. If you can lift her and there is little or no effort on her part to stand it is time to put her out of misery. If she can almost stand give her another day or three, and keep rolling her from side to side and lifting.

I have spent way too much time with downer cows that end up feeding the wolves, I know the frustration. Sometimes they can surprise you but she needs to be able to do a bit when you lift her for there to be any hope.