you should definitely complain. you don't want this happening to someone else, especially if they have to take multiple drugs. bad mix of drugs is definitely bad. although, they did corrected the situation for you, the next client may not be so lucky.
she may have had or may not have had a talk with the guy that made the error, don't leave that up to luck. take action and just file a complaint in a nice way
the kid needs to learn before a lawsuit is up his ass and may be ruining his career, and someone else's life.