Originally Posted by Wyosmith
A "service size" auto or revolver is far easier to shoot well than a smaller gun. Because there is no problem carrying a larger gun in a purse, I'd recommend a full size gun of a caliber that she's comfortable shooting. 9mm or larger. In the case of my ex-wife, she carried a 4" S&W 44 SPL and was outstandingly good with it.
Weight is the drawback here. My wife carried a Glock 19 in her purse for years. For years she complained about the added weight of the pistol and 15 rounds in her purse. Now she carries an XDs-9, and the weight reduction, according to her, is well worth it.