Board Thread:Episode Discussion/@comment-14138255-20170129165318/@comment-27082610-20170202071907

Raven is Qrow's twin sister who was on the same team as him and the only other known SEW besides Ruby. It's likely that she was extended an offer to join the Ozluminati the same time Qrow was, but rejected it for whatever reason. Salem is revealing it to people who have no ability or cause to spread the information elsewhere. Mercury and Emerald couldn't leave if they wanted to.

As far as we know, the only people that know are the Ozluminati, who have nothing to gain from telling anyone about the Relics, the Coven, who have just as much to lose as gain by telling people outside of their ranks by introducing competitors for the Relics, and Raven, who has apparently expressed complete apathy for the whole thing.