The OP seems to be asking about graduate/alumni/alumnae chapters. Not about alum of collegiate chapters being able to be reached and contributing to the collegiate chapter. The difference matters.
Every graduate/alumni/alumnae chapter has active members or they would not have a chapter. So, the OP should ask the active members; the leadership should brainstorm about reclamation efforts and reaching the inactive sisters with hopes of finding out why they are inactive, and getting them to become "members." Greek sites should never be the start or end point for such information.
ETA: I was financial and active after I graduated and am in an alumnae chapter. I know why I continued to be active and financial and I also know why many Sorors did not/are not. Alumnae/alumni/graduate chapters that have done the research also know why.
This is why I asked what kind of staff she/he is because a general answer is difficult to provide without context.