Ball pythons fast. Boas fast. Colubrids fast. In the case of balls, they can fast for a long, long time without any detrimental effects.
Unless the animal is showing signs of sickness, losing inordinate amounts of weight, etc, a trip to the vet to get a load of shot in the dark treatments will do nothing but stress the animal out even more.
..........and recommending a dose of metro/flagyl to stimulate appetite? Yeah, I know of several people who are proponents of this but have you considered that animals fast for a reason? These reasons can be as complex as environmental/security factors or as basic as the fact that most balls in captivity are eating way more than their counterparts in the wild.
Before going out and buying some flagyl ask yourself this? Are you artificially stimulating this snakes appetite because the snake needs to eat or because it will make you feel better if it's feeding again?
Why muck with her anymore? Make sure all of your husbandry parameters are correct, monitor his weight, add some crumpled up newspaper to her enclosure and let him de-stress from the vet visit. In a couple of weeks try feeding her again. In the meantime, just leave the animal alone.