You are just as excited and nervous as the 100 if not 1,000 other girls who are growing through recruitment with you. You've done your research on all the sororities and have ones you absolutely love and others you don't. At most houses, they probably won't even realize your not a freshman. You may choose to explain that you are in fact not a freshman or you may not. The reactions vary at each house when you do tell them, though. Some houses are totally cool with it and will tell you that they have a friend in their sorority who also waited to rush. There will be other houses though that find it odd that you didn't rush as a freshman. Be prepared for a lot of questions either way.
Just like everyone else you stand around nervously waiting on the first day of cuts. Other girls happily jump around proclaiming they got asked back to the max number of houses. Sadly you did not. Why? Did you do something wrong? Besides not being a freshman no you didn't. Some houses cut upper classmen it happens. There are millions of reason girls don't get asked back to a house. You'll be okay. Some sororities only take 1-3 upperclassmen total. You have to deal with the same rejection as freshmen without it really being the same. It's okay. You'll be okay. You wouldn't want to be somewhere that wasn't your home anyway.
At first, you'll be upset. Each day getting cut from more and more houses. Maybe by the end of the week, you'll have two houses to choose from. Maybe you'll only have one, but guess what it doesn't matter. There are plenty of freshmen that only get one house on pref night. You will end up exactly where you are supposed to be. Find the sorority that your puzzle piece fits into. Don't try to force yourself someplace that you don't fit. You'll find your people and your happy place I promise.
The process of going through recruitment as a junior or senior sucks. You experience the same emotions as everyone else without as many people who understand. You aren't a shiny new little freshman anymore. You know it and they know it. Moreover, a lot of people won't understand why you waited so long to rush. Whether you are a transfer student or you just changed your mind about the Greek system it doesn't matter. Your experience WILL be different from the normal recruitment experience. In reality, though, there isn't a normal rush experience. It doesn't matter if you are a freshman or a senior every girl experiences recruitment differently. If you want to go through recruitment as an upperclassman do it. Embrace the unexpected. If you have people in your life telling you it's too late to go through recruitment or it doesn't seem like you, ignore them. If you want to do it then do it because it is something that can and will change your life.