All of which means she knows a shitload more about movie making than you do.
Possibly. But if successful film credits are the metric, then other film-makers know even more about film than she does - including figures like Rian Johnson and Kathleen Kennedy. Or even Verna Fields.
I think for artistic fields, arguing from authority is weak in the first place
And if one is going to argue from authority, then I'd pick someone who seems like more of an authority in their field.
Marcia Lucas played an important role in making some of the greatest films of all time. She's the one who organized and shot the screen tests for the actors trying out for The Godfather. She was also the one who lobbied hard for Al Pacino to get the part of Michael Corleone when Paramount wanted Ryan O'Neal or Robert Redford in the role.
Her role in Star Wars is way overstated (as she herself makes clear in the Kazanjian book), but she did an Oscar-winning job by editing the last battle in a way that built tension to point where audiences went nuts when Harrison Ford flew to the rescue. Martin Scorsese, John Milius, Brian DePalma, Francis Coppola and Steven Spielberg all thought she was a great talent in her own right. Milius went so far as to say that when Marcia Lucas retired from film to be a stay-at-home mom, the movies lost one the most talented artists of their generation.
Marcia Lucas forgot more about how to make movies than J.J. Abrams or Rian Johnson will ever learn.