A long time ago, my parents had a dog that my mother adored. After the dog died, my dad had a portrait painted of the dog (painted from a photograph). When the painting was done, it looked kind of "blah" and flat. We were disappointed, but when you compare it to the photograph they were VERY close. But with the photo, it was easier to imagine the dog captured in the moment, but doing other things before/after. The painting had much more of a "moment preserved in history" feel.
I also remember my art teacher warning us never to try to "cheat" by drawing/paint from a photograph. She claimed she could always tell if a student had, because the photo "flattens" the image once and the painting flattens it again.
I have no doubt that the picture is a good likeness of the photograph he used to paint from. If I viewed them side by side, I'd probably say it was a "good painting." but I don't think it does Kate any favors. It doesn't capture the friendliness that she seems to exude. I think the expression is weird. It's neither smiling nor serious, which is just kind of a weird in-between thing.