I mentioned when I first posted about this episode that I didn't like the scene, but I think it worked for a TV audience in setting up Morgase's character for the rest of the episode. When she threatened the Amyrlin that she would come back to Tar Valon with an army at her back, my girlfriend was like "she means business!"
There were definitely better ways to do it, like I said I don't really like the scene personally, but it does establish Morgase very clearly with one scene.