Ok now I have a ? LOL

Were there certain sororities back then were if you weren't Jewish you just couldn't join or did it just so happen that most of the girls that joined a certain sorority just happened to be Jewish. I thought religion wasn't supposed to be discussed during rush and I can't imagine not inviting back a well liked girl just b/c she may happen to be a different religion than me or some of my sisters. I guess I'm just confused...