Yes, vets recommend Hill's, but honestly it is not the worst food out there no matter what you hear. I know lots would disagree with me on that. Hill's spends a lot of money on research and I have used their RX foods for certain conditions. I have a pup on Ultra ZD and he is thriving on it.
I don't advise people on diets and don't consider myself anywhere near an expert on foods. I feed my pups Castor and Pollux and it works well for the whole crew that do not require RX diets. Here is a link with information about it:
Natural ULTRAMIX Adult Canine Formula - Castor & Pollux Pet Works
As for the ear, I honestly would listen to the vet! Yes, allergies do cause ear infections in dogs.
As for keeping the ear dry, when you are using the ear meds, it will be greasy. That is ok! She needs that medicine to clear this up! Skip the ear cleaner for now and put in the meds that the vet suggested. I have a feeling that in two or three days she will start to clear up!
Good luck!