This problem seems to be all too common. Maybe you could suggest an all Greek event to your chapter. How about a dinner exchange where all the chapters at your school sign up their members (individually) to meet in small groups for a fun night out. That way, small groups from different organizations would get to know each other. It might even open up channels that no one has been able to open before!
I also remembered a great thread about two sororities working together toward a common goal. Check out
Delta Zeta Tau Alpha
Perhaps you could talk to the thread starter to find out how her chapter went about putting all of it together.
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