Hey...
I just went through the admissions process so I just wanted to mention some things.
Make sure your sister visits EVERY campus before making a decision! Without the college visit, I think one is walking on a tightrope. Before, I had never considered one college, UC Davis. But when I actually visited, my opinion of the school did a complete 180.
Also, although I am not Greek, I would focus more on what the school has to offer, in addition to what the people are like, than what the Greek system is like. As long as there ARE Greek systems, IMHO, I don't think it should be of too much importance, unless your sister doesn't want to be Greek and the school is heavily Greek.
I hope I didn't sound patronizing there! (I really didn't mean to.) Good luck to your sister!
I know how emotionally and physically draining the whole process is...I'm wishing her the best of luck!