If she will eat it when you offer it to her, just stick to an ordinary dog chow. Perhaps a more concentrated, meat based one would be best. There are so many good ones, it is hard to go wrong. I once was given a young Lab with her ribs badly showing. A couple of months of 7 cups a day of Pro Plan, and she was a fine, lean, healthy dog. So if she will eat it, just keep piling on the chow. You don't want too fast of a weight gain. Nor do you want to over do it. See
http://www.puppychow.com/products/po...condition.aspx
If she won't eat what you are giving her, post back. It may just take a day or 2 to settle into her new home. We can make some suggestions on what else to try if she won't eat dog chow. It is really important not to let dogs get into eating other stuff. It is a real project, beyond the average dog owner, to assure a dog the complete and balanced diet it needs other than by feeding a dog chow.
Some other good people here may have slightly different ideas. Good people don't always agree on everything.
I am not sure where you originally posted your question. Rickj did the right thing moving it to the dog forum where those members knowing the most about dogs are likely to find it and give a prompt answer.
And thank you for taking her. What happened is very unfortuante. We need more good people like you.