I say start with Star Wars '77 because it is the purest expression of Star Wars there is. We often forget that this was the first of everything - the Force, the lightsabers, the alien cantinas etc etc etc. I see the saga as a kind of wheel with SW '77 as the hub in its centre. Everything flows from this wonderful moment in 1977 and I think it would be cool for a child to experience it the way we did. Then, with her imagination tingling (assuming she likes the movie!), you can give her TESB, and then ROTJ and beyond…