Michonne and Andrea came to Woodbury, both were skeptical, michonne left, Andrea stayed. Governor likes Andrea, developed a relationship with her. They show what general life is like at Woodbury and the seedy undersides.
Andrea now knows much more about the governor (fish tanks, penny) and we're waiting for the show to return. Story not moving forward? Puh leeze
No, the Woodbury arc has not moved forward at all. Andrea's presence there has been entirely pointless because we've learned next to nothing about the town or the people who live there. We have no idea what general life is like at Woodbury because Andrea chooses not to interact with anyone in the town except for the governor, Milton, and Merle. Nor have we actually learned anything about the governor or the "seedy undersides" of Woodbury due to Andrea being there. On the contrary, what little we do know about those things was revealed in scenarios that had nothing to do with Andrea at all. She wasn't even in those scenes. The Woodbury arc has been very, very slowly developed in spite of Andrea - not because of her. The extremely slow development for this arc has become boring to be honest - watching grass grow would be more exciting.
That makes for a radical contrast to the excessive action with the prison arc - where the story is progressing much too fast for there to be any real development for the story or the characters. They need to find a balance in the pacing.
As for what Andrea "knows" - she only knows what the governor told her and she chose to blindly believe every word he said the first night she got there. That hasn't changed at all - and it does not appear it will change all that much in the episodes to come. They will most likely continue to use Andrea as a nothing more than a convenient plot device.