A .22M in something like one of the NAA mini revolvers will gain you significant cost over
the .22lr, but little else. A one inch barrel does not provide enough length to realize the
increased potential over the .22lr.
Get up to a two inch barrel, and you gain a bit, but not much. By the time you get to a
four inch barrel, the mag begins to show its stuff; but by that time, you could be using
a much more effective caliber.
You mentioned the availability of .22m ammo and I urge you to keep that in mind.
Even the .380 is now MUCH easier to find than .22m.
Several have mentioned the LCR as an option; I agree. If your wife is really set against
a larger caliber, at least for now, a .22lr in the LCR is a fine and fun revolver to shoot.
Once you have one of those, she may come to think about larger calibers. Move up to
an LCR in 9mm and everything she has learned with the .22 moves with her. I'll note
that I prefer the LCR in 9mm over the .38Sp because the 9mm develops its energy
faster than the .38 AND with no more recoil. The LCR in .357Mag generates far too
much fury for most people to become effective with.
I suggest you also look at several of the 9mm semi-autos. Kel Tec has some
inexpensive ones that work well (not really fun to shoot, but they work). Tarus has a
newer model in the PT111 M2 (if you get one, make SURE it is the M2) that is the very
same size as the Kel Tec PF9, but is a whole lot more fun to shoot (about $250).
Your wife, your money; pick the gun/caliber combination that makes HER happiest.
