Green’s Dictionary of Slang

(US campus) a usu. derog. term for a stereotypical sorority member; thus sue out, to dress, look and act like a sorority member.

1980		Eble Campus Sl. Fall 7: sue, suzi – girl who looks a sorority member because of appearance [...] usually a derogatory term used by non-sorority and non-fraternity members.
1981		Eble Campus Sl. Fall 6: sue, susy, suzy, soro – the stereotype of a sorority member.
1989		Eble Campus Sl. Sept. 6: susie – stereotypic sorority member.
1996		Eble Sl. and Sociability 30: Although English has dozens of particles available for word building, almost all of the examples in college slang use out, on, off and up: sue out ‘act like a sorority member, or Sue’.