friends who aren't in chapters

If you are in a sorority: If she is a freshman or sophomore, maybe. Is she cute, will she reflect positively on your sorority. Parties are run by the fraternities so for you to take a guest it would have to be approved by your sorority and the fraternity hosting the party. The other option is, she can go to parties if/when they open up after midnight.

If you are in a fraternity: Is he interested in rushing? If the answer is yes, sure most likely he can come. If he is not interested in rushing, he can only come during open rush events (where everyone is invited).

I'm sorry, but greek events are pretty exclusive. It's just how IU Greek Life is.