You mentioned that your Glock is a 9mm with a grip that's not comfortable for your wife. I'm guessing it's a G17 which is a full-size gun. You can also try her with a compact size G19 (also 9mm).
My gun is a G22 which is a full size S&W .40. That gun also comes as a compact, the G23.
The G19 and G23 are popular with policewomen. That should tell you something. Your wife (and you) should want a weapon that's popular with law enforcement. The compacts are well-known to be concealable as well. Glock also makes subcompacts in these calibers that are even smaller (and more concealable) but these may be harder to shoot.
Surely your wife can find a glock with the perfect grip size chambered in either 9mm or the more powerful .40. Either has enough stopping power to make law enforcement happy. Her gun will have to meet two criteria: 1) it's comfortable to hold and 2) it's comfortable to shoot. If either is not true, she won't enjoy practicing and therefore won't. Get thee to a gun store and have her try a variety of guns. Have her practice racking the slide in the store until she gets it right. Hint: Most happen have a lot of difficulty using the "slingshot" two finger method. There are much better ways for her to do it though.
Also, as much as it pains me to admit, there are excellent pistols not named Glock and it's well worthwhile to have her try some of those. Some of them may be easier to rack the slide. Understand though that engineering a gun that's harder to rack due to a stronger spring system gives designers more options for creating a more reliable gun. Law enforcement likes Glocks because their reliability is legendary.
Here's a very good article written by an author with impeccable credentials:
Finding the Right Fit: Glocks for Female Cops