If she ever needs to use a gun to defend herself, it will likely be the absolute most important moment of her life, and she needs to be well prepared for it, in both her equipment and her ability to use it. That means using the very best equipment she is physically able to shoot, and jumping through all the necessary hoops to become proficient with it, and learning when and how to deploy a lethal weapon in defense of her life.
You might be surprised at how many delicate and petite women are perfectly comfortable and competent with .45's, or at least 9mm's. It is a function of mindset, more than anything else, and a 97 pound weakling can shoot a large handgun as well as a 300 pound brute, with enough hard-nosed practice.
If racking the slide is her problem, there are a variety of solutions. Most of them involve technique, but working out to increase strength, or trying different pistol models is not out of the question, either, when preparing to defend your life.
Revolvers that only hold five rounds are adequate for self-defense, too, if one prefers them. Concentrate on placing the first round on target, and adding more into the same spot, as time allows, if necessary. Most of the scenarios in which a civilian has a chance to save his or her life by firing a weapon will be over in seconds, with not a lot of rounds fired.