In theory, if they're treated soon enough with antitoxin, muscle relaxant, and antibiotics, a small percentage of animals can be saved. In practice... I haven't heard of it.
That said, animals with tetanus display different symptoms than what you've described. The "saw-horse" stance, animals cannot move or movement is stiff, muscles are rigid, third eyelid is seen, etc. Hard to say without seeing her, but I'm pretty confident you have something totally different going on, and, I'll be very blunt and tell you that you really need to get off the computer and have a consultation with your vet.
As far as I remember, the winter we lost a few cows to hemmorage of the intestine (which results in black -bloody- manure), I believe we determined part of the problem was related to the hay or grain they were given. Find out what exactly's going on with this cow or you may lose others to the same thing.