Sounds similair to how my little Pygmy was when she was born----according to the woman I got her from. I think you should take this little one indoors and consider her a bottle-baby. That's what the woman I got mine from did, and I got her at 2 1/2/ weeks old, and bottle-raised her. Only one leg was a little crroked at this point, and she's fine now. Maybe you will have to help her stand a little for a few times a day-----keep us posted. I don't think this baby will survive if you leave her with the mommy.
I wish I was closer, I would come and help. I think the baby will be fine if you can get some food in her-----I used uni milk, and mixed in a probiotic and eventually mixed this half and half with whole milk from the grocery and 1 tablespoon of corn syrup per gallon.