Perhaps the most important lesson for a young girl is on her emerging sexuality- like death and taxes, the biological clock cares not if one is ready for it to strike. When a girl goes through puberty, suddenly making her sexually viable for adult men, not only does her body change but as does the way the world reacts to her. It becomes possible that the same man who had treated her with genuine care and empathy now has his own biologically-driven agenda- complete with duplicitous intentions. Watch a clumsy man talk confidently to a child but fumble nervously with a sexually mature woman- also with puberty comes power.
However, not every lesson can be taught. One learns to be patient only through experience- patience is a lesson that cannot be taught. While you can try to tell a little girl on the cusp of puberty that her world is about to change, drastically, and that this new world comes with its share of dangers, it may be easier for her to process this through the subconscious language of the fairy tale.