Thanks so much for putting up with my questions...I really appreciate it.
From your description, I can't help but think that Bella might be dealing with some severe allergies.
As someone who lives with an allergy dog herself, I can completely understand how frustrating it can be when you're trying to figure out what is causing your dog to be so miserable. I think one of the worst things about allergy dogs is that it can take years and years before a exact cause is found.
With my pup, I had my vet do VARL testing (more info here: http://www.varlallergy.com/ ), which determined exactly what he was allergic to (turns out he's allergic to ragweed and a specific type of pollen), which made it easier to control his contact with the items he's allergic to. As a side note...many, many, many dogs are highly allergic to corn and corn products, so it could very well be that if any of the dog foods you're using contain corn, that could be part of his problem. I know that Pedigree does contain a great deal of corn, so it could explain the ongoing issue.
We also began using the medication Atopica (more info here: http://www.atopica.com/ ), which helped control his itching and made him a happier guy. Atopica is sort of the 'big gun', and once we got my dog's allergies under control, we were able to switch to Temaril P instead (which is less expensive and it only takes 1/4 tablet once a day to keep my dog's allergies in check).
I think is Bella were mine, I'd start by having the vet do some allergy testing. I really feel like that will explain the majority of her symptoms.
I hope this helps.