Cynical me says try another vet
A ewe who is eating and gaining condition to me does not sound like she is dying.
A friend and I once rescued a flock of malnourished terribly neglected sheep. One went down in the trailer when we collected them. Had the vet out she had at least 5 weeks to go before lambing. This girl was so emaciated the vet could not give her an IM injection as she had nothing to inject into!
She was drenched daily, turned 4 times a day, legs flexed and stretched etc etc.
4 weeks later she stood up on her own, the following day she took herself out to the orchard and 4 days after that she lambed twins and reared them to weaning.
We were told to have her put down on day 5