Note that the portrait that is actually shown is in an infobox similar to what you expect for the subject of the article. However, I believe its her grandson, not her.
Some logic to ensure that the name of the person in the infobox is the same as the name of the subject of the article would help fix this.
That is because there is no picture for Sally Hemmings on her Wikipedia page, and DDG takes the first picture in the Wikipedia article, which would be her grandson.