My wife has pretty small hands and she gets a good firm grip on the M&P 9mm with the smallest grip insert and its been a completely reliable and accurate pistol so far. Also so far the M&P is noticbly softer shooting or just better handling than the G19 to both my wife and myself. Something to consider. If you can fit the 9mm then you can surely fit the .40 in the M&P line.
"Perfection is the enemy of good enough"