If anything, Michelle’s mom has a meaner look on her face than Michelle. And it would appear that the youngest obama daughter is following in that vein.
She did look uptight at the beginning, but did smile a little at the end.
My read is that she was closer to her Dad, and brother.
I wouldn't characterize the look as mean. But the scowl throughout the speech was clear, sustained, and noticeable in its incongruity with the moment. I'm surprised yours is the first comment on it (at least in this thread. Haven't read many.)
I don't recall a time I've ever seen parents watching a child receive an honor or perform on stage where they're not positively beaming. Even allowing for personality differences that might preclude the ubiquitous ear to ear grin most parents display at a mere piano recital, where was the glow? This was like a Marie Barone Slow Burn.