Ear infections can be very persistent, and it may take 2-4 repeated courses of treatment to get rid of them, sometimes with the same meds each time or sometimes the vet may change the meds. You will also need to be very persistent to get it cleared up.
Once my vet diagnoses a problem, I can go back for a recheck of that problem at half price, within 30 days. Don't know if your vets do that... you may want to ask them, or suggest it to them!
Does she have a lot of hair in her ear canals? This can cause recurrent infections, as it prevents the wax from being able to come out on it's own.