Just to be a pain in the ass....
My girlfriend is less picky about calibre and more picky about the gun itself. Her favorite gun is one of my Kimber's in 40SW. For her, it is the single stack grip (with Hogues) that makes the gun easy to shoot. She doesn't mind the XD9 but that Kimber is still her fav. She likes my STI in 40 (again, that one is a single stack) and my compact Kimber (although that one doesnt have Hogues) over glocks, berettas, and so on. Now, if I had a single stack 9mm 1911... that MIGHT become her new favorite.
Basically, I would find a gun first and then pick the best calibre before settling on a calibre and then picking a gun. If it is easier for my g/f to shoot a full power 40SW or 45ACP out of a single stack 1911 versus a 9mm out of a Glock, Sig, or Beretta, that should say something.... Of course, YMMV cause my g/f is a bit nuts sometimes ;-)