What message does Granny give the men through her speech and actions in "Blues Ain't No Mockingbird"?

Granny makes certain from the beginning that the men know that she is in charge of her own property. When one man casually, smiling, tries to explain to her what he'd like to capture on film, she cuts him off. She doesn't care what the explanation is, and she isn't afraid to confront these men in her yard. Cutting people off in conversation shows a sense of power and importance. (That's why interrupting is so strongly discouraged in good manners from the time kids are young.)
Granny also conveys quite a bit through her facial expressions. She lifts them as she speaks, indicating both that she questions their intentions and that she is a serious force in this conversation. When the men tell her that they like her "nice things," she replies,

“I don’t know about the thing, the it, and the stuff,” said Granny, still talkin with her eyebrows. “Just people here is what I tend to consider.”

Her facial expressions here add additional strength to the message she is conveying.
When a different man tries to persuade Granny to allow him to film her property and tries to slyly convey her permission ("Mind if we shoot . . . ?" conveys a sense that permission is already granted, almost like a rhetorical question), he is met with

“I do indeed,” said Granny with no smile.

Granny has now lost her sense of pleasantries. Her smile has disappeared, and she is not being cordial. After explaining that she is not interested in their little project through both actions and speech, she expects the men to leave.
In short, Granny conveys through words and actions that she is a strong woman who won't cave to their desires for using her property.