One way my tiny wife can operate the slide on some of "our" pistols is this: holding the pistol in her strong hand, point gun down and across her body about waist high (muzzle in safe direction, FINGER OFF TRIGGER), with other hand grasp slide over top by rear cocking serations, PUSH with both hands, as soon as slide stops completely release grip on slide (do not hold on to slide when it is moving into battery). This way will keep the pistol closer to the body and bring more muscle mass into play. It is all about leverage.
Pistols with heavier slides tend to have lower weight recoil springs, my 9mm 1911s are easier to pull back the slide than my other 9mm pistols like Glock G17, Beretta 92FS, CZ PCR. Perhaps a 9mm commander sized 1911 would be a good choice. A .380acp pistol like the SIG P238, became my wifes go to pistol (bought it for my self), when se saw how easy it was to operate the slide and how little recoil it has compared to similar size and caliber pistols, It is SA only and has to be carried cocked and locked, but she is used to it because her other pistol is a Beretta 950 Jetfire .25acp SAO. She usually cocks the hammer then pulls the slide back, that way she is pulling only on the recoil spring, and not the hammer spring too.
