Its called a cast cow when they get turned over and can't right themselves - they can even do it in a slight hollow in the dirt, or uneven bedding. Its proper name is 'Dorsal recumbency' I believe - they get turned over too far and the weight of the rumen restricts breathing and blood flow to the brain, and they lose their sense of which way is up and proper balance. They also bloat from being able to expend the gas in the rumen - a couple litres worth a minute is produced, so it builds up fast. Good thing you found her, as it doesn't take long for them to die in that position could be 5 mins or half an hour depending how bad they are over.
She will likely take a few days to get her balance back, just try and keep her on level ground and comfortable.
Cement bunks can be a real problem if cows get pushing around them, they have no traction and fall in. I knew a local dairy that was losing a few a year before they got proper guards in place to prevent it.
