My mom wants to get a pistol for her to have. She wants something lightweight, but not too small. I'm thinking 9mm caliber and about a 4 inch barrel. Anyone have any suggestions?

 

I would suggest that you take her to a gun store and let her handle the guns. See which one is the most comfortable to handle. I have an XD, I'm happy with it, dunno if she would be though, thus my suggestion.

 

My mom uses an M9, but that's been a part of her job for many, many years now.

 

Makers?

 

Find a range that rents pistols, take her there, and get her to shoot some stuff. Grip comfort isn't the only important metric, her tolerance of recoil, and what calibers and weights she's most comfortable/accurate with will become apparent pretty quickly.

For simplicity, a small (but not lightweight) .357 revolver is a good choice.

For a bit more bang, if she's comfortable with larger calibers and automatics, Glock 29/30 are pretty universally awesome and simple to operate. See also the small frame goverment-ish 1911's. I find a lot of women prefer a single stack, thin grip, and I've taught many to shoot competently with .45. Relatively low recoil, lots of thud.

 

walter PPK or sig are my favorites. 9mm or .380 - less recoil and greater accuracy. not much power but just enough to drive the bad guys away.

 

My mom has a S&W Model 40 in nickel. She's had that gun for years and I've never heard her complain about it.

 

Like the guys said, take her to a range. Do not let your opinion, or the opinion of others influence her. She needs to own a weapon that she can become comfortable with quickly. The only absolutes would be ease of use, and that the grip fits her hand.

A 357 revolver is a bit much for a first time female shooter. It is fairly standard to say that a revolver is a good choice, and that is true because they are easy to use; and because they are reliable. Nowadays however, Glock (I'm not a Glock fanboi) does set a standard for reliability, AND they carry a lot of ammo.

Just get her to a range.

 

Go to the range and let her try them out. no point to buy a gun then go the range and then she doesn't like it or is intimidated by it. My first wife could not fire a Glock without jamming the slide, FTE. Could not get enough resistance for the slide to cycle on a 9mm. Could fire a .45 Ruger with no problem but hated the recoil.
Have her try it.

 

Lots of good advice. Personally, I would enroll her in a beginner's NRA class to get the basics and build up confidence in an environment where everyone is on the same footing. Gun stores can be a terrible place with horrible advice for beginning shooters - many of the guys that work there should not be allowed to open their mouth.

After that, then I'd take her to the range.