I think that you have a great opportunity to be a leader and help this chapter grow. It sounds like you get along with these women and that you feel comfortable there. Being a member of a Panhellenic sorority provides you with so many opportunities, lifetime connections and real-world skills.
Why did you go through FFR? It was to be a part of a wonderful group of women, focusing on sisterhood, scholarship, leadership and social activities.
Many women...those who get their first/second/third choice...feel really unsure at first. I would give it a chance. Go to meetings, hang out with your new member class, connect with the older girls.
They are lucky to have you