Hey, Llonghair. It has been a long time.

I hope you're doing okay.
I'm sorry you can't be there to help out. You'd be a great advocate for your Mom after all you've been through.
By infusions, do you mean IVIG? Did she get enough fluids when she had it?
And you know what I'll say . . . get your Mom's B12 checked too! And know what the exact level is. Take a good look at her CBC, if she's had that done.
Have her kidney/liver functions been tested? Does she have any cardiac issues other than the AFib? Was the back pain a low, mid or upper pain?
So, she's still on Pred? If so, she should watch her salt intake. If they started it recently, she might not show improvement right away. Or it could be a slow, not drastic improvement. If she's still on it, I hope she is supplementing with calcium/magnesium/Vitamin D. And flax or olive oil (or nuts, if she can chew).
Does she still have a feeding tube? Why did they put one in?
Have they checked adrenal function? What about her thymus?
It might be a good idea to check all of the drugs she is on and any side effects or interactions with foods/drugs. An older body might not be able to handle drugs as well, which is one reason I asked about kidney/liver functions.
Does your Mom have obvious ptosis? Does she have lopsided ptosis, meaning sometimes one eyelid droops more than the other? If so, if a doctor pulls up on the drooping eyelid, that will go up and the other side will go down. They might go back and forth like that for a bit. It's called "enhanced ptosis" and can be one more clue that she has MG (because it's fatigable!).
Well, I hope you can figure some things out for your Mom. How are you doing?

Annie