Tasmania?  (Forgive me if I just made a bad joke.  I don't follow events of that part of the world.  And I hope anyone from New Zealand can for give me for deleting their nation so irreverently.)  

Age.  Yes.  15-17.  I have done this twice now.  Both times we have opted for just having completed High school.  Seems to be a common choice.  And it is probably the best one.  Gives her a chance to complete a normal childhood if she had a decent family.

So far I have also opted for your character discovering she had a younger half sister who has grown up Atlantean, giving the current quen a more (evil?) stepmother role.