I bought Mary a Taurus 9mm. It has a decocker. Small enough for her purse, big enough not to hurt when she shoots. Mary is only 5'3" and fine boned. IIRC it is a 24/7. Since she goes by "Mary Kay", I thought pink was appropriate. They did have them in black.
This stock (meaning from the company) picture of the gun has the longer of the 2 mags it shipped with. The other fits flush to the butt.
Modern 9mm defensive hollowpoints don't play 2nd fiddle to the 40 or 45. While some women need to be shown the "trick" of pushing a semi "away" from the body to cock it, instead of pulling the slide, I think a 9mm is the minimum I would do. They even have double action only 9's
Some of the Kahr 9mm's would be appropriate also.