Well I will say it again just for good measure, feed your snake in its home enclosure. No reason to feed it elsewhere. You are just asking for a bite by moving it.

The bite was probably feeding related. Either that or what others have said, you just freaked her out.

Ball pythons really don't bite that often. If they are scared they are much more likely to curl into a ball then to bite you. Just learn to read your snakes posture. Don't be scared to handle your snake because it bit you once. Since you have been bit, you should know it really isn't a big deal

They don't normally bite once they are out and moving around or flicking their tongue. They also don't strike when they are all balled up.