The Coen Bros. first drew up a draft screenplay for True Grit some years ago. I imagine after No Country For Old Men won a heap of gongs and an honorable horde of dollars, it was rather easy to get the film into production.
They promised that they'd be true to the source novel's point of view and have Mattie Ross be quite definitely our lead character, not Rooster Cogburn, and as you'll see from this teaser, they seem to have been good to their word.
Good to their word, to my eyes and to my ears.
I'm sure they quite deliberately included the iconic reign-in-mouth moment in this teaser trailer to get people talking. Guess this paragraph proves their point.
Check the trailer out at Apple if you can, for the best quality.