Shapeshifting isn't common among all dragons, but quite a few of them learn how to. Then again, not all of them particularly enjoy interacting with humanoids or smaller creatures.

[ He knows this from personal experience. ]

And dragons tend to be willful, stubborn, and prepared to go to great lengths to ensure their own success and to accomplish their goals. I'm not surprised that she's apparently done much to shape your world. It's in their nature.