There are several questions and answers on this subject, but for the sake of getting you pointed in the right direction, here is some things to consider.
Anyone considering carry of a weapon for self defense purposes needs to ask themselves several very important questions.
1) Are you willing to put in the work to know the weapon inside and out? How to safely use it, store it, clean it and maintain it. This isn't something that you put in a gym bag or a purse and just slide it around from time to time as it gets in the way. You have to be willing to take it to the range, practice with it, practice reloading, practice shooting from different stances - in short, practice, practice, practice...
2) Are you willing to use it should the need arise? Too many people are willing to carry a weapon, maybe pull it at a time that they feel threatened but are unwilling to actually pull the trigger, which doesn't do anyone any good. Each person has to ask themselves if they are capable of pulling that trigger and living with the consequences. If you can't honestly answer that question with a yes, then you need to consider some less lethal technologies.
3) What is the size and abilities of the person in question? If your woman is 98lbs dripping wet, she probably doesn't need a handgun that is going to jar her senseless when she pulls the trigger. What is her background with firearms? Has she ever been to the range? Does she have limited experience? She could have the best firearm in the world, but if she isn't familiar with it, it won't do her any good when the time comes to need it.
All that taken into consideration, if you want a blanket solution:
A revolver, preferably hammerless, is a great defense choice for anyone, but especially a female who is not well versed in firearms. Everytime you pull the trigger, it will go bang and it's very reliable. There are few moving parts to worry about, and it doesn't have the "dangers" associated with carrying in "Condition 1" like with a semi auto pistol.
Outside of that, it becomes a personal preference for the shooter. A standard response from a lot of people is the Walther PPK/S variants, but I don't like those choices, especially for women, because they are blowback operated and if you limp wrist the weapon it may not cycle. But, to each his/her own - which is why there are so many fabulous toys out there to begin with.
Best of luck!