Madame- Educating others is the best ammunition, so if you can get Bombalurina's pamplets and spread the knowledge in any other way that would be great. Taking in the unwanted fish would be awesome! But of course, you will be limited as to how many you can take.
For your friend with the goldfish in particular, is there any chance you could make an excuse to keep the fish for a week for her? Spring break is coming up, right? Any chance you can keep her fish? After a week of your care, you may be able to prove the difference of good care to her... Just think, if you return her fish happy and swimming and in a clean environment, it may convince her she's wrong.