It's not a gang. It's a club.
Seriously, though, lots of countries have Free Masons, so if the country has Masons, I'd explain that it's a fraternal organization for college women and college graduates, sort of like the Masons.
If they don't have Masons, I would explain that it's a club for college women and college graduates that does a lot of philanthropy work and sometimes offers housing to its members.