I have an FNP-9 and a Beretta PX4 Storm. My wife and daughter who are each about 5'4" and have small hands can handle either of these with ease. They both rack more easily than a number of pistols I have tried and both have interchangeable backstraps to accommodate smaller hands.
Once you start going to smaller guns chambered for 9mm, you start running into more recoil, which your wife may find objectionable.¡¡