The folks on the boards here have a saying... "Never let the sun set on a down cow."
Because of a cow's size and weight, nerve damage is very easily caused when they're down for extended periods of time. Also, 1st calvers are prone to problems -- if a heifer were to go down spraddle-legged she could easily break her pelvis, whereas an older, mature cow would be unlikely to suffer the same type of injury.
If you have access to a tractor (which you evidently do) then get a sling or set of hip-lifters on her and get her up. The less time spent down the better. As soon as is possible, I'd give Vitamin B complex to help with nerve damage and cellular restoration, and Dexamethasone or Banamine to help with reducing inflammation and pain.
Best of luck with her.