[astroAPhi]

I would definitely agree that you should go to an advisor. They are impartial and should be capable of sitting down with a girl and telling her that she needs to shape up and stop treating others poorly.

I think that just about every chapter has some sort of sister who goes about the wrong way of treating others. In my experience, these sisters usually end up eventually being ignored unless they really know how to intimidate (which it sounds like this girl does). While no sister should be ignored, sometimes it's the best way to let them know that they're not getting through to others properly.

I won't kid you, individuals like that can tear your chapter apart. I really urge you to talk to someone higher like an advisor as soon as you can.