I don't like to take anything for granted. So I will ask...
Did your mother write a rec? And do you have recs for the other three sororities?
Being that your mother has stayed active, I am sure this was taken care of.
Also can you tell us what school you are rushing at? WE LOVE RUSH STORIES!!!
I am sure you will be fine, and will find your home. Greek life is great. I understand you are nervous, but that is a good thing. It means you understand what you are going through. Trust me there are going to be some girls completely unprepared for rush, they will think it is just like joining any other club in high school. And you will benefit from knowing what to expect. It sounds like you are ready, and won't have any problems.
Please remember to write and let us know what happens!
Good Luck! 