I will echo what was said: a wheel gun is probably your best choice as it does offer simplicity of use. Now here's another thing: take her to a range where they rent guns. Have her try couple different ones and see what she likes best. Buyin a gun without testing it out it's like buying a cat in the bag. You take it home, open the bag and you decide you don't like it and it's not for you. If she is to have any use out of it, she should be familiar with it and like to shoot it (however frequently or infrequently it might be).
On the other hand: if you guys will start shooting occasionaly then start considering semi autos. Why? The shorter pull of a single action (ok, if you go DA/SA first pull will be like a wheel gun but rest will be short) will make you more accurate of a shot then a double pull. There is something to consider though: under stress you don't want to accidently shoot too early but on the flip side under stress you don't want to miss by accident.
Anyways, if you want to go shooting and can make it to OC, gimme a holler. I got a membership @ a range where they have a wide variety of handguns to try. All it'll cost you is the price of their ammo (you can't bring your ammo if you want to shoot their guns).