According to the Panhellenic Unanimous Agreements which all the 26 NPC sororities adhere to....
"A woman who is or who has ever been an initiated member of an existing NPC fraternity shall not be eligible for membership in another NPC fraternity." (
http://www.npcwomen.org/policies/sel...agreements.htm)
I believe the same rule holds true for IFC fraternities. Way back in the day, you could join as many sororities as offered you bids. Then NPC got together and decided that membership should only be offered to non-affiliated women, hence the above statement. If you are unsure of whether the group you are wishing to join is in conflict with another, check the lists of NPC groups and IFC groups at
http://www.npcwomen.org/memorg.htm (for NPC sororities) and
http://www.nicindy.org/member_frat.htm (for IFC fraternities)