I'd say that such a trip was our of their purview unless maybe they thought planning and support was so poor that her life was in obvious danger, but not if it was just a principle thing.
From what I gathered of the film, it was all of the principle that a 14-year-old girl isn't capable or responsible enough to do such a thing.
She and her father had the trip and boat all planned out quite well and the evidence of the trip proved it too. She did a magnificent job and played it safely too.