The girl you are no longer friends with could certainly stand in the way of you receiving a bid to her sorority.
If you absolutely can't handle being rejected, don't rush. You are going to be cut by sororities throughout the process, especially due to your being an upperclassman.
Also from your "location" being Houston, Texas, it is really late in the year to be securing recommendations... Please go to Houston's Alum Panhellenic Web site:
http://houston-panhellenic.org/. There is some good information on their web site about recruitment. If you have any questions, please contact the AP Recruitment Chairman, Mary Anne. She's very nice and is good about getting back to people. (She has a new email addy; don't know if it has been updated on the site. If you have probs getting in touch with her, PM me).
A junior does not have as many opportunities to join a sorority as an underclassman, and this will account for cuts in the earlier rounds of recruitment. Be aware of this and don't freak out if you only have a few invitations back after the first round.
It's not you; it's your class rank. And possibly, a low GPA.
At this point, if you go through formal recruitment, you should stick it out through the prefs round because this could be your last chance to join a sorority... and you should be very open to joining any of the chapters on your campus if you desire sorority membership this late in the game.
Good luck with whatever you decide to do. There is going to be rejection in this process. But if you really want to try sorority membership, formal recruitment is a good place to start.