One big issue with women and belt holsters is that most women are "high-waisted", and this means that a pistol caried in a standard OWB concealment type holster will often place the gun butt almost under the armpit, making it impossible for her to get a firm, "shooting grip" on the gun while it is still in the holster, and creating no end of problems in drawing and reholstering for those who are both "short-waisted" and big-bosomed! (we can chuckle over this, but it is a very serious problem for women who are required to carry on the belt) This can be dealt with by dropping the holster in some manner so that the gun butt rides no higher than the top of the belt. If she has wide hips, she will need a steel shank in the holster-drop so it can be bent to allow the butt to be vertical and not poke her in the side.
IWB holsters are much less forgiving, and even those that place the butt relatively "low" are still going to have it above belt level. I know female IPSC shooters who will actually cut off and reposition belt loops lower on a couple of pairs of pants for shooting use, but that is not a "real world" solution to the problem. Look for designs from well respected makers that indicate they are made with women shooters in mind...hopefully they have addressed this issue so you won't end up spending money on several different holsters before you finally find what she needs.
I am curious if you have ever thought about a Robar grip reduction on a G19 for her?(yes, I DO know what a woman who has made up her mind is like
but I also predict she may have some problems with a reduced-size 1911 design, especially as fatigue sets in during a class)