I am glad you were there to save her from such grave danger, care for her so lovingly, and can give her a loving home in the event she truly needs one. It is sad to think anyone would treat such a baby so badly then turn her out when she grows old, but I know it does happen at times. If she is merely lost, again, you have helped her immeasurably, regardless. There are some decent canned food products that she should have no trouble eating, and she will find her own exercise routine if nothing more than following you everywhere...which my Yorkies do!
I believe she will reward you for your kindness with her sweet, immense love, devotion, and loyalty.