there are plenty of greeks in law school. i knew plenty of sorority presidents where i went to school (big campus) and they had to deal with eating disorders, sexual assaults, drug problems, budget concerns, etc. being a stupid social chair won't help you out, but being your sorority president probably will. it will show your commitment to an organization (you don't just wake up one day and get elected president but have to get active in the e-board your freshman year, right?)... so put a positive spin on it and relay how your presidency reflects positive aspects of your character (commitment, determination, etc) and how you learned what you needed to change.
if you were the tri-delt president at UF, under no circumstances should you mention that you hid your korean girls (and fat girls) during rush so that the rushees would think that the DDD were all blond and blue eyed skinny girls.