There is no such thing as improvement in the short term if it is menengial worm. If it's menegial worm the only thing the antibiotic is for is to keep pnemonia at bay with the cool weather (here the humdity) the pennicillin I wrote about is to treat listerosis. Has the vet treated sucessfully menengial worm? The high dose of Ivermectin I would give right now, it is the only wormer that will cross the blood brain barrier to kill the larve living in the spinal cord that is cuasing the paralysis. If you can treat her before she goes down her outcome in the end will be much better.
But if after treating her with the thiamin which you should give every 4 hours, by the 3rd shot if she is better you are not dealing with menengial worm but polio.
If she doesn't get better by her third shot of thiamin, and you have continued with the biomycin, dex etc...you will have to get more agressive with the dex and add banamine also to pull her through this. Dexamethazone if that is what he gave, has likely already slipped the very early pregnancy so treatment should continue then deal with the pregnancy later, if he gave her banamine and not Dex, I would get Dex....perhaps blood test her to see if she is indeed still bred in 2 more weeks.
I want stuff like this treated agresively in my herd so that I get 100% mobility back, having a doe weak in her rear end that can't hold up bucks, does't have the muscle tone next year to push out kids, is worthless for me, I would put them down rather than have a dibilitated goat.
It just doesn't seem likely it is MW since you don't have white tail deer on your place. Keep up the thiamin shots, I bet she turns around by tommorrow morning. Vicki