Why would Andrea just trust that Michonne had a "good" reason to kill her man????? He's only treated her kindly, so why would she not defend him when she sees her ex-friend about to slice him in half? Andrea does not know how evil and messed up this man is; she doesn't see what us viewers see, and the fact that Michonne never reveals anything to Andrea-- not of her suspicion that the man murdered the Coast Guards, that he sent a team to murder Michonne. That's extremely sloppy, poor writing and character development for Michonne.
heelsonfire: I think the fact that it's revealed to us viewers that there's a huge gapping hole in the rear of the prison may be foreshadowing of things to come-- for better or for worse. Rick and his team obviously haven't discovered it yet, and that exposed threat is for us to know and anticipate. That is good writing, whereas the Michonne never revealing very important information other characters so that they may discover it for themselves is poor and extremely sloppy writing.