[honeychile]

Just a minute... Your sister & roomie was insulted back at Homecoming and you're still associating with these clowns? That's NOT how it's supposed to work!

As Senusret said, you most definitely need to tell these guys, in writing, exactly why you as a sorority are upset, and what you expect them to do about it.

Something on the lines of brothers have insulted your sisters on an ongoing basis, but the racial slurs were beneath the dignity of any mature college student would be good. The brothers involved should apologize to those they have insulted, and a public general apology for their lack of class and/or tolerance could be demanded. The letter should be written in a mature, nonemotional way, with a copy sent to their national headquarters.

Until these are fulfilled, you as a sorority should not continue to associate with this fraternity. Yes, that sounds drastic. But it works.