What is she vaccinating with and how often? Both enterotoxeamia and pasteurella can cause sudden death, and there may not be that many external symptoms...
I have had a goat kid dying within less than 24 hours, only sign was some diarrhoea at lunchtime (but he was up and about all afternoon), by the evening I noticed that his pupils were not dilating as it got darker in the shed, but was sure he did see me. took him to the vet who didn't find anything wrong with him. Gave AB's and AI's - but he died next morning being in horrible pain and screaming. It was awful. And he had been vaccinated in the summer with a double shot of Lambivac... so this year it seems that there are more deaths (also heard similar for lambs/sheep) which point to clostridial and/or pasteurella (not sure if this one comes under clostridial) disease despite up-to-date vaccination.
Maybe our animals are just under enormous stress due to this constant bad weather, no sunshine to speak of etc etc - also possibly causing lack of vitamins, grass/hay quality is not very good... so many reasons/possibilities
Not sure if PM on enterotox is usually conclusive, we only do a PM if a second animal dies under similar circumstances.
I have re-boostered all my goat kids with Lambivac and also given Ovipast+ to all my goats, including the adults. Not re-done the lambs and doing a head count every morning... so far all still there.