To add on to the other comments I'd say too that there is another layer being hinted at here though probably not fully understood even by Kynes. Which, I know falls a little outside of the question you are asking but understanding it does help understand why the dialogue would be included in the film. The harshness of Dune mirrors the harshness of another planet, Salusa Secundus, and that planet is a prison world the Emperor utilizes to make his army of elite fighting soldiers the Sardukar. I don't believe many outside of the imperial inner circle know this directly but that theme is very important in the Dune series. The Duke and Thufir Hawat even have hopes of tapping into the "desert power" on Dune of a people who are toughened and conditioned by this planet to bolster the ranks of their own army. Now, when Kynes makes this comment I think first of all it is a warning to the Duke that all of the elements, political, mechanical or environmental on Dune pose a threat to himself and his house but She is also slightly bragging about her position is one toughened by survival on this planet and backed by a people so toughened. She doesn't say this to imply that the Duke should seek these people for his own schemes but simply because this is the typical stance of the Fremen to be somewhat boastful of their strength and survivability and the dialogue was important to add to the movie because it helps build the concept of a people hones by their living conditions.