I'm sorry about things not working out.
I don't know where you go to school or what campus life is like there, but I agree with whoever said try alumnae initiation. I don't know much about that or national sororities in general, but I am sure if you check the web with a group's national site, you might find information there.
Have your tried going local? Are there local sororities on your campus. I have seen some that cater to older members. Check out the localsororities site at
www.geocities.com/localsororities to see if there are any in your state/school/etc.