Well, of course nothing is impossible, but Fuzzie Alum is absolutely correct in letting you get perhaps a glimpse of the work ahead!
I suggest some serious reading asap:
www.npcwomen.org
This is the site for the National Panhellenic Council, the governing body for 26 National, Social sororities. There are links to the national sites of all 26 organizations, I suggest you take a look at each and every one. Especially if they offer a thorough history page.
http://www.nphchq.org/
This is the site for The National Pan-Hellenic Council, the governing body for the "Divine Nine," or the nine, national, Historically Black Sororities and Fraternities. Their histories are fascinating as are all the descriptions of the major work they have done in all areas of service.
http://www.nicindy.org/
This is the North American Inter-Fraternity Conference site. This is the organizations that serves 66 national, social fraternities. Excellent reading here as well.
None of these sites will provide you with the "blue print for going National" in addition, no one here can provide you that in a single post either. The sites above will provide you with a starting point from which to do some basic research. It just seems that you might want to start your research into the possiblity of national expansion by seeing what fraternal organizations are already existing and thriving on college campuses today.
A google.com search for Christian based sororities will lead you to a number of local sororities that are structured like yours. It might be a good idea to contact some of these groups of like- minded women and ask them if they have ever considered expansion.
Another thing, I assume this desire to expand comes from not only the collegiate sisters, but an alumnae base who feel that there is a need for such a sisterhood on college campuses everywhere? An Alumnae group who are passionately dedicated to this project and can commit their time, resources and finances will be essential. If such an alumnae base does not exist for you yet, I would begin there by contacting them and letting them know of your plan.
Good luck with your research and with your goals,
Greek Love,
violets