I think it could be done.
Kelly makes a good point about grad students often having thesis, TA or RA positions, jobs, spouses, and kids to think about... If you found a way to create a sorority with a lower time commitment than a typical NPC sorority requires of its active sisters, it could fly. Say, chapter meetings every 2 weeks instead of every week; several small charity fundraisers instead of one big one (each sister can participate in each fundraiser as she is able instead of stressing because the sorority's one big charity event is at the same time her thesis is due); etc. In other words, fewer hours that you "must" devote to the sorority, but just as many opportunities to "choose" to devote your time and energy.
Good luck
