Was she though? Who would have told her? She has probably only ever seen bettas in vases and as decoration. I mean, where have you gone and seen bettas being treated properly? Most pet stores aren't exactly set up to show them off in nice, elaborate tanks. Most people I know who have them are the betta murderers we all would be (and some have been) without this site and research.
Unfortunately their proper care really isn't common knowledge. Just like most people don't know to feed premium quality dog food, or that tanks can be set up with a Ammonia-Nitrite-Nitrate cycle. Most people probably think that Nitrates are things found if hot-dogs, if they even know that! You can't fault someone for not knowing what most people don't know or ever care to know.
Remember that the tank your fish lives in is his or her's whole world. Ask yourself this question, and answer it honestly: would you choose to live there?