Tara,
I'll let you know something that it took me a while to figure out. At one time or another,
everyone is insecure. As you have discovered, freshman year and recruitment are two of those times. People behave very differently during stressful, new experiences. This might explain the type of behavior you have seen demonstrated. Don't allow the behavior of other people to change your feelings about greeklife. Go into recruitment with an open mind, put your best foot forward, and enjoy yourself. Good luck!
As for your mother, give her all the information about how many successful women are in sororities. Show her the NPC website and the websites of greeklife at your college and their chapters. I suggest that you save some money so you can pay your way.