Do a little physical therapy several times a day, moving the joints and very gently holding them closer to the correct position for a few seconds at a time....just to the point of resistance. The selenium will help. I'd give her the rest tomorrow and some more B's.
The doe needs it, too. Too bad your vet didn't know that. Probably because goats are so specialized and vets learn next to nothing about them. I suspect the goat section consists of, "This is a goat. Avoid them at all costs."

The baby would not be deficient unless the doe was pretty much depleted. The babies are favored over the mom, so if there was anything in her to give, the babies would get it. So she is dangerously low, too.
I just got in from giving my other pregnant does BoSe shots and they all got B vitamins and are on the Red Cell regimen, too. This is also important in keeping worm levels at bay, as mineral depletion leads to worm overloads, especially this time of year.
See how much I've learned in the past year?

Nothing like a crisis to get me to sit up and take notice! My three black does were all black 2-3 months ago, then BAM! Copper deficiency in the two Alpines who were preggers. Started with a new batch of lovely horse hay that is not lovely goat hay, but all I could get. Most hay here is from heavily fertilized fields, which can also lead to or exacerbate deficiencies.