hey girl
i PM'd you. i am a muslim in a sorority as well and although I think of myself as somewhat liberal, I am quite modest in what I wear. For my preference two years ago I wore a dress from ann taylor that came to a few inches above my ankles. I felt a LITTLE bit odd because everyone else was wearing shorter dresses but it was not something that my house held against me
i think the key is to be COMFORTABLE in what you wear because if you feel that you are out of place, others might feel that way too and perceive it as you not wanting to be there.