A little background- I carry a P320C daily. I'm confident, comfortable, and most importantly accurate with it. My girlfriend got her CCW late last year and decided on a P365 after trying a handful of similar guns. She is slightly less confident than she wants to be but also has not practiced at the range since COVID.
As noted, a .22 conversion kit is awesome and a non permanent solution without a large investment.
In the last few days, she has gotten a bug to buy another pistol. I totally support this. She wants a .22 because they are cheap and have less recoil. I think we should get a larger 9mm for the house that is easier to shoot (being larger) and a better defensive caliber.
Suggestions..... and GO!
Well there's a flaw in your thinking here... Hitting a target with every round from a magazine (10) as opposed to 1 or 2 out of 10 provides marginally more "DEFENSE"... 9mm isn't a solution to providing "more" or "better" of anything.
What does that is... repetition, which in turn... becomes skill, muscle memory, more and mostly fun!
So don't knock the .22... Shooting it provides the basic skills needed and magnifies errors with shooting because you eliminate a lot of the bad stuff, like anticipation, recoil, etc., and focus on the things which affect your shooting.
Go .22 because that's what she wants, and because she'll enjoy it and thereby entice even more shooting.
Just my $.02
Good Luck