One of the photos Vivian Meek Bibler sent along was of our great-grandmother, Alice McSherry, as a young woman. Vivian said her family also thought Alice looked rather forbidding or at least not what we’d call happy. Well, she was a schoolteacher at one point. They do have to carry some authority, don’t they? (I expect to be scolded on that aside. Vivian is a retired teacher herself.)
I would lay some of the expression to the reality of having to hold a pose for several seconds without moving or even blinking.
You choose which interpretation you want, or even suggest another.

As for the elaborate dress, we should remember that her mother and one sister were milliners, a leap away from Joshua’s roots in Quaker plainness.
Well, the times were changing, even for that Quaker discipline.