I can’t wear the Pros because they never stay in and this applies to every rubber tipped earpod.
Gen 1 fits like a dream. Gen 3 fit a bit differently and you can feel them in the ear but you can wear them forever like this. For me they don’t fall out even when running. So gen 3 is the answer for me.
Also the audio quality is superior to the Pros because you can’t have noise cancellation and transparency mode without some effect on the music. That did it for me - the sound and the loudness.
Take a look at her ear. If it is longer vertically than horizontally she may be a good candidate for the Gen 3. If her ear is more like a circle and the first gens are snug then she may have a problem with gen 3.
Everyone’s ear is different. I have not been able to wear any of the AirPods that fit into the ear canal so I have always used the Airpods. The Gen 1 AirPods would fall out all the time. Just bought the AirPods Gen 3 and they fit much better for me. The sound quality is much better than the Gen 1 units who‘s battery was about shot.
Ears are like finger prints and all are different so it is hard to tell if your wife will like the fit. I do agree with another and the shape of the Gen 3 is very close to the Pro units.