I have no firsthand experience, but from what I have read on here, sometimes colonies like to take older girls for many reasons. These girls know the campus well, and will soon be alum and therefore build up a strong alum organization quickly.
My advice for you is to be yourself! Smile, have fun, and get to know the girls.
Good luck! I am very excited about our 175th chapter, and I can't wait to hear more from you.