I have an update for you -
The nearest alumnae panhellenic to you does not currently have reps from the chapters at the school you're attending. (per the delegate from my group) So, they will not specifically be able to assist you in getting a rec letter.
They suggested that you try contacting the local alumnae chapters from each sorority directly for assistance, as they don't have the contact info. (Which is what aopirose suggested earlier also.)
Not exactly a
great update, but at least you know and won't waste time attempting to contact the panhellenic group again.