Once again whomever is dressing Michelle has a good eye for color, but a terrible eye for line. The color is nice with her skin tone. The belt with a bow emphasizes her tummy and the straight back shows her rear too much. There are ways to help disguise tummy and backside (I know - I have ample of both) and her fashion advisors are not doing their job helping her with this.
The dress is too short for a woman of her age at an event of this nature. And going sleeveless is simply not formal enough for a state event.
A 4 x 8 sheet of plywood would hide most of her ‘ampleness’.