And Daenery needs to fly over to the north and have a look for herself to see what is going off.
My prediction is that the season will end with the White Walkers breaching the wall somehow and Castle Black falling. Whether or not Danny will be in a position to do anything about it or not remains to be seen. This show love to take 90 degree turns when you least expect it, so I doubt the circumstances of the coming battles with be predictable.
But who can command them? They only listen to Dany and it's not like she took some person and said to the Dragons "Listen to them until i return" At best they would naturally fight against anything that attacked Dragonstone but one can't be sure.
Tyrion had a line last season where he said some Maesters believe dragons are at least intelligent as humans, if not more. Doesn't mean they *think* like humans but they do appear to be able to recognise people and know who and/or what they're supposed to be breathing fire on when Danny yells "dracarys". I mean people sure, that's easy. The move and smell like uncooked lunch; but ships and wagons? A dumb animal wouldn't be smart enough to distinguish them from rocks and trees. So they should be smart enough to guard their territory.
What surprised me is that she has so much combat skill.. Syrio's training was incomplete and she received further training with the Faceless Men but their main mode of operations is infiltration and stealth so it came a bit surprising when Arya went all Captain America on Brienne.
Remember that she did get a lot of single combat training and even learned to fight blind, which is how she defeated the waif. Also, she spent a lot of time cleaning dead bodies. That's a good way to get a very intimate knowledge of human anatomy. What the soft spots are, where the muscles and ligaments are vulnerable, how far a joint can pivot. All very useful when seeking to disarm or disable an opponent.
Also consider she's had more than just two teachers over the years. Syrio taught her to move, Yoren taught her to fight smart and use her emotions, The Hound taught her to fight dirty and pick you opponents, the Faceless Men taught her to use her senses and of course Jon Snow taught her to stick 'um with the pointy end.
