Super odd that they started with prednisone and plan to use it long term. You can NOT just take her off. She needs to be weaned. As the dose decreases, the peeing and drinking will.
Cytopoint shuts down itching. It should work to help that.
Apoquel works to modulate the immune system.
My vet started with Cytopoint with my dog. It's the best.
Per my vet and most documentation I've read, aqoquel has very few side effects. However, my dog developed weird growths while on it. They were the first test site in our county and have have prescribed it for years with no issues. My dog used it short term for nasal congestion due to the allergies when antihistamines didn't work during trial season.
Sounds like you did allergy testing already. Did they talk to you about immunotherapy shots? I thought giving the shots would be terrible but it's easy. It's not always successful though.