I don't know the reputation of Tri-Delt at USC, but I can tell you that your sister should go into Recruitment with an open mind. The Tri-Delt chapter at USC may be quite different from the chapter on which she's basing her opinion.
Please refer your sister to this site, to read up on Recruitment and related information on choosing a sorority.
http://panhellenic.tripod.com/FAQ.html
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Fraternally,
Barbara
Zeta Tau Alpha Alumna
If you have to go around telling everyone you're in charge you're not much of a leader.