The NPC website has lots of information. Send her to
NPC Parents
We all know that there are girls who fall apart when they join sororities, but it doesn't have to, and in fact doesn't for the vast majority of members. If they did, the sororities would fold faster than we could get them started up. The reality is sorority membership leads to better grades, better leadership experience and vital socialization (good life lessons). And the other fact is that there are plenty of college students who torpedo their education because of too much partying. This is not a mutually exclusive issue.
If there are any Alumnae NPC events in your area, maybe you can talk your mom into going so she can get a more realistic idea of what it means to be a sorority woman.