The overall impression created by the writer about the woman is that of being courteous along with being straight forward; and also someone confident and comfortable in her skin.
Explanation:
The writer describes how the woman greets him (them) with politeness, but at the same time keeps a straight face which indicates that even though she may be approachable she is not one with whom anyone takes chances or cross boundaries with.
She shows respect and expects the same from others.
She is also described as being tall and large-boned, along with unique skin color, i .e..mahogany, and dressed simply.
This indicates that the woman does not mind the way she is and makes no efforts to cover up her skin color or the way she looks.
She is dressed as simple as possible and is yet confident about herself.
She is one who gives respect and commands the same from others.