Without seeing the snake it is hard to tell if she is going into shed. Not feeding could be a sign of that. So is loose skin. Balls can look downright ghastly before a shed. The fact that she seems to be plumping up is a good sign. With any new snake, a trip to the vet can be a great idea, especially if you are a virgin with a species. Short of that, I would put in a humid hide. If she is in shed she may well start spending time in there. With Balls sheds can happen really fast after a growth spurt, so if your snake just started getting enough food and is putting on weight a shed is to be expected.
David