Good point. Once they're eggy, they're eggy until they drop the eggs.
Since she was a Wal-Mart betta, she could have a mild internal infection. Epsom salt could help with that but since the bloating is returning, it's not being very effective right now. Go ahead and keep her in the epsom salts at her current dosage but let's see about treating the infection. Do you think you can find Jungle Labs Anti-Parasite medicated pellets? Petsmart sometimes sells them. The medication in the Anti-Parasite pellets is effective for internal bacterial infections as well. The trick is getting her to eat them, because they don't taste very good. You can soak them in garlic juice for a few minutes so they get good and garlicky, that might help. You may also need to crush them into smaller pieces.