ForeverDiamond, I don't know what your "house" arrangements are, whether you each have a room, a suite, or a house. One thing that I think works well is the Midterm & Finals Study Break. We would put out a coffee urn & keep it filled with water, and have instant coffee, tea, creamers, sugar, sugar substitute, hot chocolate, disposable cups, spoons etc at the ready. If anyone has some cookies or fruit, all the better! Declare ONE HOUR for a study break, and have all the Greeks in. It's amazing how y'all will pull together over that common problem - tests!!
FWIW, we did this just for sororities, since there were 9 sororities in one building, and didn't allow men. That way, everyone could come in comfy clothes, glasses, no makeup, slippers... well, you get the idea.
It also gave us a reputation for being good hostesses - which made our alumnae so happy, they often provided the goodies!