Poor Bella.
Did the vet suggest putting Bella on a allergy medication or at least something to get the inflammation under control? I assume she's on a antibiotic to get infection under control as well?
I would think about what Bella is eating, what she is eating out of, where she is playing, etc and try to eliminate as many allergens as possible. For example, if she's not eating grain free food or if she's eating food with poultry in it, those are two things bulldogs are commonly allergic to. Also, if she's not eating out of steel bowls, you might think of changing that. Using fragrance and dye free detergents to wash her bedding, keeping her from laying on grass are other ways to see if you can get to the root of what's bothering her.
I have not personally done it but I know others have had their bullies allergy tested to see what exactly is bothering them. I understand this can be costly however, if the allergies are severe, it might be worth it.