Corina,
I totally agree with James! You have done so much, and you should not limit your options so early in the game -- continue to write to groups.
For example, you should also look into and write to non-NPC sororities! You may be surprised and pleased at what you find. Going with a non-NPC sorority would enable you to go national and have the support and sisterhood that your group wants -- all before the founders of your group graduate!
There are several non-NPC sororities out there who may be very happy to accept you as a colony. Both Kappa Beta Gamma and multi-cultural sororities, like Theta Nu Xi, have sisters who post on greekchat. By searching on the internet, you can also come up with at least a dozen or more non-NPC sororities that are general, multi-cultural based, religious based, etc.
Remember, looking for a national group is like job hunting... there may be rejection letters, but if you keep interviewing and networking you will find what you are looking for!
Luis