Have the same issue with my GF. Tiny hands. She has issues with my XD45 as you described. The issue is the double stack mag and the width of the grip. Has to reach around it pull the trigger. We have been looking at the following for her(all are single stack):
M&P Shield(loves it!)
Beretta Nano(close second)
Taurus 709 Slim
She shot the XDS and the Bersa Thunder as well, but hated them. Didnt like the Rugers or the Walthers at all. To blocky according to her.
Good luck in our search.