Had this asked in one of my classes, my simple answer was and is, I don’t pick out my wife’s shoes and I will not pick out her gun she has to like the feel and fit.
That is unless you like it and you know your wife will put it down and then you can claim it as yours.
If she might be a little timid, I'd even start her out with a .22 and let her get some good practice with that before moving up to a larger caliber. But the best thing is to rent a few and let her decide what she can handle. You don't want to start her out with something that is too much recoil for her making her think she can't be good at shooting.
__________________ Honor Student: School of Hard Knocks To the world you may be one person, but to one person you may be the world. Quando Omni Flunkus Moritatus
Yup I agree go to a range that will rent you a few guns to try but let her handle them and pick out what feel best in her hands , what you like may not fit or feel good in her hands , start her with nothing more than a 9mm to get a feel for shooting it . I will say one thing the bigger the gun the less muzzle flip it will have and she will be more comfortable shooting it at first , this will go away once she gets a few hundred rounds under her belt then she may be more comfortable shooting a shorter barrel and may not be a issue . I see alot of women shooting the Ruger SR9s they are pretty skinny in the grip area , also let her shoot a few revolvers thats the route my wife went , she just likes the feel and the looks of a wheel gun so thats what she picked out