She is a lucky goat that you found her.
I would see if you can get hold of some of the Dectomax, or evan some Spot On which will also help get rid of mites/lice. Make sure she is wormed, and really she ought to be dosed for fluke too just in case. Don't let her out on any of your pasture or with the other goats until she has been wormed.
If the weather is nice with you, you could give her a bath. There are special shampoo's you can use, but to be honest, either fairy liquid (well mixed in with some water) or a mild human shampoo will do, as it's too help get dust and mites out, and so that you can brush out her coat.
As others have said, don't give too much hard food to begin with as she probably isn't used to it. Hay, water, ad lib, small amounts of concentrates. Little extra meals if you can manage it of soaked beetpulp, alflafa to help fatten her up a bit.
Beth