Hi nolesgirl. It sounds like you are doing a great job of being proactive in finding recommendation letters. Great job! I think you are on the right track trying to locate a contact from your hometown Alumnae Panhellenic (APH). One place you might want to try (if you have not already) is the NPC directory of APHs:
http://www.npcwomen.org/alumnae-panh...directory.aspx. Now, many times a local APH will start a website or facebook page and not tell the NPC group, so it is also a good idea to search on facebook or google for the group as well. If someone is not responding to e-mail, then you might want to try calling her. While I know that many people do not have home phones these days, there are still a few of us "old school" folks that do. So, I would try the phone book next
As far as finding other recommendation letters from friends, you might try searching for various NPC groups Facebook fan pages, and then looking in the right hand corner of the page to see if you have any mutual friends. It might not work, but worth a shot. Even if your FB friends are collegians, they may be able to help you in recommending local alumnae from that sorority. Don't stress out about it - just do the best you can!
I think a short e-mail saying that you would like to send her a thank-you note, and ask her what address she would like you to send it to would be just fine. IMHO