I believe that this may be another Tetra like situation. She bears a striking resemblance to Ocarina of Time's Zelda, but as you can see, she and Link appear to be friends. Link is apparently trying to find his lost friend, and as you can see in the trailer, she obviously get's herself into some trouble. I think in the initial beginning of the game, she will might not be Zelda yet. Or, she will through some hardship, become princess of Hyrule due to certain events.
I think it is a very good guess that she is a more simplistic looking Zelda whom is also Link's friend he is despairingly trying to search for. Then again, she may be just a friend of Link who has no connection to Zelda other than hairstyle resemblance.