[chickenoodle]

I would definitely call the school and see what you can find out. I had to call a SUNY branch to find out which sorority my grandmother was in and I found my contact extremely helpful. I called the school's alumni office, but since you are looking for information on an organization perhaps the library might have archives accessible to a non-student. Maybe you'll get lucky and find some pictures of your great aunt with her sorority!

Good luck! I sincerely hope you find something.

ETA: I did a little search on Google and Delta Phi Gamma popped up. It was the name of a local chapter in Quebec, Canada that FIJI chartered (absorbed? Not sure of the word I'm looking for). I'm not saying it is the organization you are looking for, but I thought it might be helpful, especially since there was a FIJI chapter at Marietta at one point. Please keep us posted.