I just became a chapter advisor with only two weeks left in my graduate program. If the opportunity had presented itself any earlier, I would have turned it down. Graduate school is a tremendous time suck. I don't know what your program/specialty is, but if you're a full-time graduate student, you can probably expect to put in something like 30-40 hours a week on reading and assignments alone.
There will be other opportunities for you to take on a more involved role as an alumna, but for now, concentrate on your studies.
