I would recommend the Ruger LC380. I have a number of compact 380s and this is by far the most comfortable to shoot. I also have the LCP which is a bear to shoot but super easy to conceal.

Check out a Kahr. I have a Kahr 9mm and my wife is able shoot it comfortably. It is a single stack so it is a little narrower. I am able to carry it while I work in a restaurant without it getting in the way at all.

Find a gun range with a good choice of firearms to 'rent' at the range. Have your wife try the different size grips, plus shapes.
My wife has very small hands, she prefers not to have the fingers grooves as many times they do not fit her fingers well. She has an old two piece Pachmayr compact J-frame grips (thinner than the new one piece ones, significantly so). An S&W J-Frame is her choice and 38 Special 90 gr FTX® Critical Defense® LITE (pink box) greatly reduces recoil. J-Frames are easy to find from .22LR, .22Mag, .38 Cal, etc (even .327). Pistols also have many calibers.
Have your wife try both pistols and revolvers (thumb positions/gripping are different, for revolver having someone who uses them showing you will allow a better evaluation, my personal experience has been many are not familiar with revolver handling ~ many YouTube videos).
It matters not what anyone else carries, it is important what your wife is comfortable with, both with grip and recoil effect and revolver or pistol (semi-auto) and weight (usually, heavier relates to lower recoil but more noticeable in carrying every day, it is a personal decision). If she is not comfortable with it, she will not use it.

Find a gun range with a good choice of firearms to 'rent' at the range. Have your wife try the different size grips, plus shapes.
My wife has very small hands, she prefers not to have the fingers grooves as many times they do not fit her fingers well. She has an old two piece Pachmayr compact J-frame grips (thinner than the new one piece ones, significantly so). An S&W J-Frame is her choice and 38 Special 90 gr FTX® Critical Defense® LITE (pink box) greatly reduces recoil. J-Frames are easy to find from .22LR, .22Mag, .38 Cal, etc (even .327). Pistols also have many calibers.
Have your wife try both pistols and revolvers (thumb positions/gripping are different, for revolver having someone who uses them showing you will allow a better evaluation, my personal experience has been many are not familiar with revolver handling ~ many YouTube videos).
It matters not what anyone else carries, it is important what your wife is comfortable with, both with grip and recoil effect and revolver or pistol (semi-auto) and weight (usually, heavier relates to lower recoil but more noticeable in carrying every day, it is a personal decision). If she is not comfortable with it, she will not use it.

I am a female and carry HK VP9. I love it and find it extremely comfortable. It comes with 4 different interchangeable pieces in order to allow you to customise the grip completely. Your wife could adjust the backstraps and side plates to the most narrow and it would be fantastic for her!
http://hk-usa.com/hk-models/vp9/

My wife really likes her Ruger LC380. It has the same frame as the LC9, but has very low recoil. The dimensions are about .8 " longer and taller than the Ruger LCP/LCP 2, but it is not near as snappy as these smaller guns.

Lady Smith & Wesson

My wife carries a S&W M&P in 22 LR.

HP25A- its a Phoenix 25acp regularly available here at Buds for under $135! With ten round magazine. My wife loves it!! Almost zero recoil too. My wife hated shooting until she fired the .25acp, now she's hooked!!

There are so many choices ... I would suggest going to a range and renting a couple of different ones, maybe based on what the range personnel suggest, and let her try them out. Some people have very different perceptions of what is acceptable recoil and what isn't. You may end up with a 22 Mag, or even 22 LR, neither of which is a preferred caliber for self defense, but both of which are better than nothing. Good luck in your search.

I highly recommend a Glock 43 or a Smith and Wesson Shield 9mm. Both guns are very slim, and have surprisingly little recoil. If you want to go for a smaller caliber I would suggest a Beretta Tomcat in 32 ACP.