These very small pistols need stout recoil springs to function properly.
It isn't uncommon for folks to have problems operating the slide: particularly folks with less than optimal hand strength.
Although the spring will lighten up a bit with use, it needs to be pretty stiff. I'm unaware of an aftermarket recoil spring that is both noticeably easier to operate and also ensure proper function.
Your relatives may benefit from learning, and practicing, a different technique for operating the slide:
grasp the slide with the weak hand by grabbing the slide over the top with thumb pointed toward the shooter (for a right handed shooter, this means that the left hand finger tips are grabbing the right side of the slide while the left side of the slide is grasped by the base of the left thumb) then pushing with the dominant hand in firing position while pulling the slide to the rear with the weak hand then letting the slide slam forward by releasing the weak hand.
Sounds more complicated than it is.