I suppose all allergens have been identified, and those that can be avoided are being avoided? Has she been placed on a food trial? Is she on a hypoallergenic diet? Is she on daily Atopica? Have you tried nasal sprays?
I have a feeling that your dog may also have some airway disease, such as a bit of allergic and bacteria, or viral bronchitis and/or pneumonia and if this is treated concurrently with antibiotics as well as the other medications that she is currently taking, it may help to control all. I have some dog's who can never go off their medications and must use pulse therapy, which is a high dose of medication for one week out of the month and than dosing Monday, Wednesday and Friday for the next 6 weeks or so, than going back to a full dose when needed, for example.
Your dog may also benefit from acupuncture and herbal treatment, and holistic modalities, as an adjunct to her traditional therapies. Holistic therapy may also help with the side effects of the traditional medication, such as acquired Cushing syndrome from steroid use.
You can find a holistic vet in your area by googling for one and also from the international veterinary acupuncture society, American veterinary acupuncture association, American holistic veterinary medical association, Chi Institute for vet acupuncture and herbal med, etc.
has she had x-rays of her lungs and liver to make sure they are ok. i had a shihztu who had same problems, it was his heart and lungs , he had allergys most his life took everything yours is or was on, he took predsone for years made him really big but only way he was not sick, it gave him cushings to, so have them check that out . i know what the drugs do to them and now i have a 10 week old girl so if she itches i go into a panic , dont want allergeys again . good luck with your baby.