Had the first two been Macgonnagle and the Defense Professor, then the rest make a bit more sense in that the Defense Professor urged Macgonnagle to do whatever it took to get Harry off his current path, and, well, Harry had just lectured her about how responsibility works, and so she was in a state of mind that demanded action.

That said, you're totally right: continuing to throw potential emotional bonds at him to try and cheer him up wasn't the best idea, at least not so soon. Surely Macgonnagle is smart enough to know that Harry knew exactly what was going on, and would therefore be less receptive? It's a general trend when working with stubborn and upset people, and I imagine this is no less true among Hogwarts students, and thinking about it for five seconds should have made it clear that it'd only be worse with Harry. I suppose she couldn't think of anything better to try.