I think your sister should call her doctor and have him call in another prescription for cefuroxime to a different pharmacy. If she has good insurance, insist that she wants the brand name. For 20
Ceftin tabs at Walgreens (online), the price is $86 - 20 generic tabs are $67. Not much difference, and your sister can be sure she is getting the correct medication.
Personally, I would never return to the pharmacist that made the mistake about the
amoxicillin - he should have known that amoxicillin/clauv is a penicillin antibiotic. Pharmacists are supposed to catch serious medication errors and interactions based on ones medical history.
And the re-labeling is sloppy and unprofessional. If it's not already illegal, it should be. I would not trust that pharmacist at all.
If your sister doesn't want to change pharmacies, how about asking for the pharmacy manager and explaining the situation re the amoxicillin and also showing him the re-labeled container? That pharmacist needs to be disciplined or fired, and your sister should complain before more harm is done.
If your sister decides to talk with the manager, she can also insist that she be shown the original container that the cefuroxime is dispensed from (probably a large plastic container holding 100 or 500 pills). That container will have the manufacturer's name on it, etc. The manager can then show your sister tabs from the container, and hopefully those tablets will match the C 250 imprint. Then insist that 20 fresh pills be dispensed in a new container with a correct label.
Sorry, I didn't mean to write a book, but this is a scary situation.
Best of luck to your sister.