Hi!
As a member of a USF sorority, I would say that there are several factors that would influence your getting into a sorority. First, for the most part the only way anyone would know if you were a senior would be if you mentioned it to someone. While I know chapters drop across the board for things such as grades, etc. after the first day, I know from past years some people went through recruitment and it wasn't until they mentioned they were an upperclassmen that anyone was aware of it. With 500 girls going through recruitment and only 7 sororities there's ALOT of people to meet! and remember
Therefore I offer you this advice, don't mention that you are a senior unless specifially asked. And then if you are planning on five years, you can say something like, well technically I"m a senior but I won't be graduating this may. Also, There are several chapters on campus who have taken older sisters before, both in terms of chronological age, and in terms of age in the university. Having been on campus for three years, is there a specific organization that you are interested in joining? Because you could probably find out their contact information and email/ call the executive board and express your interest (without being overbearing).
Also, talk about what you can offer to the sorority and what you can bring to their sisterhood, on this board we often talk about quality over quantity, and I know that I would rather give a bid to a senior who was going to improve our chapter if only for one year (and as an alumni) then a freshman who was only interested in meeting boys and partying, and would disaffiliate after she obtained what she wanted to do
If you have any questions please feel free to PM me!!!!
Hope it helps!