Hi Mate
I have several older air rifles
177 and 22 caliber
My children leant firearm safety and rifle handling on them. The 177 is an old thing, short, and light so it was easy to hold and aim.
My humble advice is, decided what the air rifle will be used for, that is, hunting of just target work at the range.
Take your wife to the local gun shop and any other gun shop in your area to see how she feels holding different rifles, what's the fit like, what's the trigger like.
If the rifle is for her, them she must decide with your help of course.
Air rifles are great for plinking, no recoil, hardly any noise, so cheap to feed (If you get a beak open or lever style). No experience with co2