So by Tom's logic (oxymoron?) the Big 6 are:
By number of chapters: Alpha Phi, Chi Omega, Tri-Delta, Delta Gamma, Delta Zeta, and Zeta
By number of initiates: Chi Omega, Tri-Delta, Theta, Kappa, Pi Phi, and Zeta
Of course all of those numbers are constantly changing, so the Big 6 must be a rotating term. Whatever.
Tom, I think we all know what she meant.