Proper humidity levels in a glass tank can be a pain in the rear to maintain. Since you know she is going to shed you make a hide (container that contains damp sphagnum moss for example) and allow your ball python to enter. This type of hide will have higher levels of humidity than your glass tank. Also, there is a "sticky" in the caging section of this website that goes through step by step how to regulate humidity levels in your snakes glass enclosure. Basically, you use foil and duct tape and make a vent hole so air can circulate throughout the tank. This can hold in humidity more effectively.

As for feeding your ball python during a shed I think that is up to the snake. I have heard that they will not eat druing a shed but mine has yet to refuse a mouse during her shed. Try and feed your ball python and see what happens. If it doesn't eat I would not worry about it.

Are you using an under the tank heater or are you using your above cage heat lamp to get your temperatures to 90 degrees? A heat light will suck the humidity right out of the cage. Although it is good to have your snake on a day/night type schedule they do not require specific lighting as they are nocturnal snakes.

Good Luck!