IMHO, if you do not now more than leading and feeding, you should not be rescuing horses.
Yes. "Head-shy" means literally what it sounds like. A horse that is shy to have its head messed with.
A common thing inexperienced people do with head-shy is not mess with their head. The more you mess with their head, the less head-shy they'll become.
Another common thing inexperienced people do is try hold the horse's head down and force them to accept. This will not work. That will only make them more head-shy.
Make soft, slow movements around her head at first. Do not try to hold her head down. If she pulls away, do not lower your hand, as this releases pressure and tells the horse that pulling is the right answer. If she makes even the smallest lowering of the head, lower your hand and step back. This is releasing pressure, which tells the horse that lowering the head is the correct answer. This goes back to the saying, "Make the right thing easy (release) and the wrong thing hard (pressure).
Continue doing the method of pressure and release. Your goal right now is not to touch her head but to get where she doesn't pull back. Once she gets more comfortable, try stroking her cheek. This way, she can still see you and your hand. Slow, soft strokes. If she pulls - pressure and release. Continue to softly stroke her cheek until she get comfortable. Then work on moving to the for forehead, more sensitive areas, and harder stroking pressure.
Note: When you stroke at first, make it soft enough so she can feel in, but not so soft that is feels like a fly and irritates her.
My horse can tell you more about me than I, myself, can.