That's so awesome you want to rush while getting the degree you need.
I would recommend to focus on what grade you are in school-wise -- that you are almost a sophomore, because that shows you will be there a while.
At my chapter (Zeta Tau Alpha at UW in Seattle) being 23 looks kinda different though; we still took a 22 year old junior one year, but I heard rush is a lot harder down south. Just make sure you are prepared for a hard rush, and DO NOT get disappointed!
Get as many references as you can, visit alumnae chapters; there are listings on most national sorority websites. I'm an RC this year, so my advice is to just be yourself and have fun; it all works out for the best!!!