Well, she is the Queen of Storms, so it is quite possible. I don't know for certain.
The way to verify it is send her to battle alone and have her cast Storm Power as first action. If that happens several times, then she does autocast storm.
I tested it some more. She doesn't autocast for sure. But when she spends a couple of turns in a province the storm appears and stays there as long as she does. I had a storm in the battle even without her - I cloud-trapezed her away.