I will make it legal!
I simply applied logic to the situation: If we, here, learn to drive at age 16, why wouldn’t someone in Star Wars learn how to fly as a coming of age thing? Luke did, as a farm boy. Wedge did, working his parent’s gas station. Why not Leia, a daughter of privilege? She can handle firearms, she basically takes over her own escape from the Death Star. She survives torture. She BEATS torture, actually. Later we see her on speeder bikes, fixing the Falcon, shooting more dudes, and so on. It’s almost insulting to suggest she can’t fly an X-Wing, the Rebellion’s fighter of choice. -- Brian Wood, writer of Dark Horse Comics' latest Star Wars title, Star Wars, which aims to rewrite the Star Wars saga as if An New Hope was the only source material.
I suppose one could say that as a major leader of the Rebellion, she was too valuable to risk her life in near-suicidal raids on major Imperial bases like the assault on the Death Star... but even that breaks down when you consider that she was down on Endor with the rest of the raiding party. And hey, we've got plenty of fictional precedent for the leaders of small groups of fighters saddling up with their crew, from President Bill Pullman in Independence Day to Admiral Adama in Battlestar Galactica. And now that we know there were female X-Wing pilots... The conclusion seems unavoidable.