Okay, this might not sound totally PC, but here it is.
I would counsel any woman who has a problem with alcohol, drugs, anorexia, bulimia, etc. to really think long and hard before joining a sorority. If she is prone to fall to the temptations, then she will have to be very careful about where she pledges.
Every chapter is different. In some chapters you would rarely find these things a widespread problem. Are there individual sisters with these issues? Yes. But the chapter as a whole doesn't subtly and not-so-subtly encourage them.
There are other chapters where a woman struggling with these issues would be walking into a very unhealthy situation.
Can you tell from the outside during recruitment what the chapter is really like internally? I'll leave it to others to debate that issue. I just know if I had a daughter or a friend's daughter who was thinking of recruitment and who struggled with these issues... I don't know if I would encourage her to rush. At the very least I would have a REALLY frank conversation with her.
My two cents. Your mileage may vary.