First off: Welcome to BP.net
An open air enclosure with hardware cloth sides sounds like it would be a nightmare to keep proper humidity levels in (at least 50% at all times)
As others have said Ball Pythons like smaller, secure feeling enclosure. Something where at least 3 sides of the enclosure are covered and there are hides on both the cool and warm sides of the enclosure. Preferably you want both hides to be identical in order for you BP to never choose security over thermoregulation.
If your BP is not eating I can think of 4 possible things it may be:
1. Husbandry is not right. Is her warm side over the UTH about 90 degrees?
2. Your BP does not feel secure and is stressed.
3. The former owner was mistaken and the BP is eating mice. You might want to try a live mouse and see if you get some interest.
4. Your BP is simply not hungry. Older BP's can go a long time without eating. During the breeding season my males typically don't eat for about 6 months with no ill effects.
Also to increase the chance of you BP eating try offering the meal during either dawn or dusk. In the wild this is usually when BP's come out look for food.
You also may want to check out the BP.net caresheet, it has a ton of useful information:
http://ball-pythons.net/forums/showt...s%29-Caresheet