Sounds exactly like the position I was in just over a month ago.
Malnourished, dry, cold snake with tons of leftover shed.

Tracking weight is more important than length. You could have a nice 4 foot gal, but if you don't know how much she weighs, you won't know whether or not to give her more food or just how healthy she is. Try weighing her every time you feed her. Plop her on that scale (in a box so her doesn't get away) just before you feed her and write it down. That way you can track how much weight she's gaining as she recovers. Tracking sheds might also be a good idea, to help you predict when she'll shed again.

Unfortunately, you should also keep an eye out for respiratory infections because it was so cold in her previous tanks.