I like all these ideas but I'm also in the same boat as you. My wife situation is almost identical and she's actually a darn good natural shooter. She even took her snap caps and gun into the garage yesterday and dry fire practiced without my prodding for a change!!!!
I say the .22 is a great idea for revolver and point shooting, intuitive close range shooting because it naturally points perfectly on target with the hand compared to most pistols that point slightly downward. Never the less the big difference for my wife has been her past history with a very nice browning semi-auto 380 I bought her in the 80/90s that jammed with half the ammo we bought and just befuddled her all the time.
So for that reason she's owned a Taurus light weight snubby 38 for maybe 10 years. Bedside gun, you can shoot 38 in it and 38P. So that has allowed me to buy mild ammo she can practice with. Recently I bought her a S&W version of this gun which is way way better, the 442 which is the covered hammer version, as you probably know.
Now I've bought a body guard 380 she likes semi autos agains suddenly, and her small hand fits around to the trigger better than the 442 snubby 38 with it's long stiff trigger. She does feel safer with the stock trigger pull. But she also LOVES the thumb safety on the bodyguard.
I would say 22 is the best starter but honestly if you can't afford to buy a lot of guns those 22s can be more expensive than just buying her the final solution and focusing on dry fire practice. If she wants to endlessly plink on the range, outdoors and save money on ammo, heck yes. But if you have a tight budget I'd say buy one of these newer generations of carry guns and get her directly onto the personal defense wagon.
My wife is already developing her point shoot abilities and can nail targets at 7 yards without using the sights (combat accuracy). That's farther than any distance she is likely to ever shoot in our home or in self defense. But I have been starting her drills MUCH close than that (important). One last note. I own an LCR by Ruger too and they have the one benefit of a trigger that's smooth as butter. One thing I like about revolvers is they simply WORK and less picky about ammo and cleaning. And the grip activated laser comes on for her without the need to intentionally press a button.
By the way another alternative is to buy one of those S&W revolver BB guns, they even have bio degradable BBs and she can set up targets in the yard and practice drills. I have not done this yet, but considering it and the 22 idea.
In either case good luck, sorry for the rambling.