We have not heard much about Moghedien so far, but I can only assume that she works by getting others to do her dirty work. It would seem that she knows precisely what the Black Ajah are searching for but does not want to compromise her safe position by being too obvious in drawing their attention to it. I can only assume that she expects them to uncover it eventually and she will then hang around whilst they use it, waiting for the perfect time to take control. Perhaps, if they are totally incompetent and spend far too long unable to find it, she will eventually start dropping hints or otherwise poke them in the right direction. However, I imagine that she is a very patient person and will be happy to wait for them as they bumble about foolishly.