Here are a couple of suggestions
I think some or most universities have philantrophy rounds as 2nd round. Be sure and ask the sister specificly after you have said your hello to tell you all about their philantrophy and the activities that they do to raise money or support that philantrophy. The sister may start on this first but for me personally I loved when I was asked this question. If you have done previous volunteer work you could add your comments in as well.
Another good one is "Could you tell me about your sisterhood activities?" "Sisterhood is very important to me" (or whatever your own statement would be)
Also I think that something that would be impressive would be to "Please tell me (if you know I suppose) about the alumnae programs etc your sorority offers for involvement after college" Or "What ways are there to be involved in the sorority?" (ie offices held, directors of events etc)
You may have to re-word some of these b/c these were just my general thoughts. I think its great to ask questions in rush. I hope this helps...
