Reminds me of my CCW class last Sat, the instructor was showing pros and cons of different guns.
He explained the ultra simple design of the revolver, you can hold it any which way and shoot it, there's no slide to worry about, FTFeed issues, stove pipes, tap/rack/bang drills, etc. just keep pulling the trigger and it goes bang, if it doesn't go bang, pull the trigger again, and it will probably go bang the next time, etc.
Whereas there are certain issues if you train w/ a semi-auto to practice to make sure if you're under fire you can handle a problem. Then he went on to show some other things about certain models. So there happened to be a guy in the class w/ the certain model berretta (or knock off, not sure) that was like the one in the Jackie Chan movie where he disarms Chris Tucker by completely removing the slide w/ one quick action, and the instructor did the same thing. It was cool, coz I didn't know there was a particular weapon w/ that vulnerability, I thought it was just tv magic.
Then he asked what people thought was the most reliable semi closest to the revolver, etc., some said glock, he knows I have a glock, we're all unloaded and double checked unloaded at this point btw, and he asks me to hold the weapon in a ready position over his shoulder pointing behind him, and pushes on the slide taking it out of battery and tells me to pull the trigger, and of course no click. I don't know how many semi's that works on, I would assume a lot, but I noticed on one of the shooting shows last night they actually had a rail attachment that blocked the front of the slide/barrel to prevent this very thing. Then he asked what would happen if someone put their hand in front of a revolver and you pulled the trigger (if you don't know, it would put a big hole their hand!).
He admittedly carried semi-autos, but was pointing out the benefits of a revolver for some users.
So, to recap on a serious note, like others have said, there are tactics either mechanically disable a weapon, or physical maneuvers one could use to protect their weapon, or potentially disarm another, but it will all depend on your knowledge and PRACTICE of them, and the opponents knowledge and practice of similar or counter moves.
And I would bet that in an armed defensive position distance is your friend, but if you're unarmed you might have a better chance to confront him at close range, unless you can stay really far away and he's not the greatest shot. In any case, I'm betting a lot of luck and divine intervention has a lot to do w/ survival for the avg citizen in that case, and that non violent person would have to take some serious training to rely on disarming a suspect while unarmed, good luck w/ that. I want to take some other training w/ and w/out firearms, but I still want the firearm
And she should seriously think about taking some firearms classes and read some too, even though she doesn't like guns, at least she could become moderately knowledgeable, and be able to tell the difference whether some guns are loaded, at slide lock, what the suspect would have to do to reload, or some other vulnerability, so that she would know when to take action, if there was a choice, since timing in an attempt to disarm someone while unarmed may be a critical factor, she should learn more about guns, IMO (maybe she'd decide one wasn't bad to have around after that education too!)
Karz