The Beretta 92FS is a pretty good pistol, but it is a large pistol and the grip is huge. It might not be the best choice for a woman but only a trip to a gun store will confirm. There are compact and single stack versions as well, so check those out while you are there. The Beretta in my experience is very reliable when keep clean. But mine have been kinda fussy when they get dirty so clean often and use a good lubricant.
If you are just looking for a house gun, I would recommend looking at the Ruger P95. They aren't pretty nor are they fancy, but their reliability is on par with the Glock, Beretta and Sig, for a price that can be less than $300 (especially with rebates)!
If you demand something a bit more refined, I'd take a look at the Sig-Sauer P228 and P229. These are very nice pistols with grips that seem to fit small and large hands alike, they are reliable and they have outstanding accuracy. If you don't care to spend money on a handgun, this is what I would get if it fits your hands and your wife's.
I would like to recommend the Browning Hi-Power, but most women don't take well to single actions. None-the-less, the Browning (or FN) Mark III will feed well with JHP's, sit in the hands like a dream and are accurate. These are probably the most natural pointing pistols ever made and anyone who has held one knows exactly what I mean.
The Glock 17 and 19 are another choice. If I bought one I would make sure it wasn't one made in the "E" Series run, as some of these had a problem with the frame rails breaking. And the 9mm Glocks (the original ones) seem to be the most reliable and trouble-free. They are simple which is what makes them so attractive. Just draw, aim and shoot.
The verdict is still out on the Springfield XD's as they haven't been around all that long. But from what I have seen so far, they are every bit as hot as the Glock. I haven't heard these pistols associated with all the "kaboom" stories that deservingly or undeservingly surround the Glock line of pistols. I would say these are a winner.
The H&K USP compact might also be a good choice for your wife. These guns come in a zillion configurations, so be sure to carefully check what controls and conditions each pistol has to make sure you get the model you want. These are very high quality, accurate and reliable guns....but like the Sig's, they are pricey. But when trusting your life to the reliability of your gun, cost shouldn't be an issue.
And last, let me give you some ammo advice. Try to get a gun that will hold up to +P ammo so you can shoot the excellent 124 gr + P Speer Gold Dots. This is about the best performing ammo there is readily available to civilians. The Winchester Ranger 127 gr +P+ and the 147 gr standard pressure are probably tops if you can find them. These are made and marketed to law enforcement by Winchester but not directly sold to the public. But if you look hard enough you can find them. The NATO 124 gr 9mm loads and equivalent (namely Federal M882 and Winchester white box...sorry, cant remember the product number) are loaded hot and shoot to the same POI as the +P loads. These would make for some good target practice at a cheaper price. Avoid the Federal Hydra-Shok and most of the other JHP's as many either clog up with fabric from clothing and don't expand well or some don't penetrate well enough. Stick with any of these following loads as they meet the FBI minimum standard of 12" of penetration and expand robustly, even through heavy clothing. These loads are:
Barnes 105 gr JHP Copper Bullet
Triton 115 gr +P JHP (#TR9HVA)
Federal 124 gr JHP (LE9T1)...not the Hydra-Shok
Speer 124 gr +P JHP (53617)
Winchester 124 gr JHP (RA91P)
Winchester 127 gr +P+ JHP (RA9TA)
Federal 135 gr +P JHP (LE9T5)
Remington 147 gr JHP (GS9MMC)
Speer 147 gr JHP (53619)
Winchester 147 gr JHP (RA9T)
And oh yeah, one more thing regarding defensive ammo. Test it to make sure it functions well in your gun! And then practice, practice and practice some more! No bullet design can make up for poor shooting, so make sure your wife trains until she becomes proficient in shooting, operating and maintaining whatever gun you decide to buy. Good luck and report back when you make the final selection!
-Charging Handle