First of all, I don't really believe even the daughters of a military Colonel would be wearing silk, even for petticoats...personal opinion only.
Second, look though I might, I've never found any of Cooper's characters saying, "...because the French haven't the nature for war...their Latin voluptuousness combined with their Gaulic laziness, and the result is, they'd rather eat and make love with their faces than fight."!
Yep, the movie follows the book all right!!???!???
And I'm the Queen of France!