It is a very common herb in health food stores. Don't let any health food store talk you in to cranberry capsules either. Studies have shown that the capsules do not work the same as pure cranberry juice or blueberry juice. And the juices do not kill the bacteria, they only prevent bacterial adhesion. Uva ursi kills the bacteria.
So it is definately okay if she is on any other drugs. I get the impression she is on lots for different stuff.
Sorry, I forgot to answer that when you asked earlier. It must be taken at least an hour separate from her medications. Uva ursi is also high in tannins that can lock up medications or other herbs rendering them useless.
Her flora must be non existent with all the anitbiotics she has been taking.