AZ-AlphaXi explained this well, but I just wanted to add (as I'm from a campus whose Greek system gets compared to the University of Illinois a lot) to make sure to tell your daughter to keep an open mind throughout the process. I think it's easy early on to have some favorites, but tell her to try to not form too strong of attachments or opinions until at least second rounds (or 7 party day, I don't know their specific terminology) and, if she can, not until preference. I think this will help her keep her feelings from getting hurt if she can withhold judgment until later into the process.
Hope this makes sense. Best of luck to your daughter and if she gets placed tell her to make a username and join in on the fun! We'd love to know if she gets placed. Best wishes.