When we have a sick goat, I find giving them willow branches helps them recover and start chewing the cud again. Not easy to find willow, but river banks is a good place. Ours eat the leaves, which are just coming out now, the branch and the bark. It has pain relieving properties in it. I have found it a life saver on more than one occasion.
She is probably being sensible having a small amount at a time - its like us after an upset tummy, you take it easy foodwise, don't you?
Will she eat Alfa A which I give to my horses - the goats love that. Its a fibre feed and although you do not feed a lot, is good. Puts weight on my old horse anyway!! My bigger goats are always lanky looking, so they have sheep nuts and that helps the weight loss too. Soaked sugar beet is good to get weight on too.
You need to get the weight on gradually, not piled on suddenly. And I assume she is no longer milking, so I would not give her a massive amount of got mix at one meal.
If she only eats a little at a time, perhaps you could give her three smaller meals, if thats possible. Maybe she will digest it better?
Lots of hay, if she will eat it too.
Hope your goat is on the road to full recovery soon.