Be aware that any device that raises the comb 3/4" will also cause the gun to shoot higher. It may well cause your wife to shoot over everything she shoots at. It drops the heel farther into the shoulder pocket, but at the same time raises the muzzles and changes the whole eye to rib relationship. While it may well put the butt lower in her shoulder pocket, it may cause her to miss everything by shooting over it. It's a poor answer to getting the butt lower in her shoulder pocket, IMO.
A device like that linked to by builder can accomplish what you want to do without changing the eye to rib relationship, but at the cost of being ugly as all get out. I have something like that on my Perazzi, that I use for competitive sporting clays, but I'm not concerned with aesthetics with it .............. only breaking targets. I wouldn't put one on a SKB S X S, but that's just me.