Regarding milk fever:  If her nose is dry and ears are cold, certainly could be milk fever.  But that is pretty uncommon with beef cows.  In dairy cows it usually occurs around birth but before 72 hours (unless the mineral portion of her diet is really screwed up).  If this cow showed signs of nervousness (not mentioned) than grass tetany would have been a more likely possibility.

Let us know what your vet says.  Thanks