My wife is looking for something with less recoil than her 9mm. If a 9mm is 100, and a .22 is 20. where would a, .25 or .308 fall in between 100 and 20?

Recoil, or perceived recoil has more to do with the type of action on the pistol than it does the frame size. Weight also makes a difference when comparing the actions.

Blowback - Most small .380's like the Ruger LCP, Taurus TCP, Bersa Thunder. The barrel is fixed in place. The case when fired pushes against the breach face. These typically are also harder to rack the slide on, especially for smaller shooters, because they have stiffer recoil springs to slow the slide down. This increases the felt recoil because the slide starts to move immediately after firing transferring all the energy straight back.

Locked Breach - Walther PK380, Glock 42. The barrel, like on full size 9mm, 40, and 45 Glock/XD pistols tilts down when the gun is fired. The camming action of the barrel takes the initial shock out of the recoil and allows the use of a lighter recoil spring making it easier for smaller shooters to rack the slide and reducing the felt recoil because the slide has to cam the barrel down before the slide can recoil backwards.

So why does my G35 smack into my hand so much harder than my Para 16-40 with the same load? It has everything to do with weight and grip design. In the case of the Glock, the Para weighs half a pound more. Look at revolvers. When shooting the same load out of a Super Blackhawk and a Super Redhawk, the Redhawk is going to hurt worse.

Sig p238 380

Does she want something to carry or to shoot?

Buy her a heavier 9mm for shooting at the range.

My daughter went from a Glock 23 to a Springfield XDM Compact in 9mm. Her groups tightned up very well. This is her carry weapon also-I know its a bit bulky for some but that is what she shoots well

YMMV