Is she pulling the hair out herself do you know? Is she biting or scratching the patches at all?
Have the vets suggested possible causes or the next route of care? Blood tests, biopsy, skin scraping?
Have you done any research on the internet into possible causes or into the medication you have been given, to see what it is commonly used for?
If this vet can't help any further do you have another you could take her to for a second opinion?
Sorry for all the questions!
It could be a number of things really; ringworm, mites, an allergy, the list goes on. My dog had two bald patches on his flank in exactly the same spot on either side and it just turned out to be a hormonal thing!