My 2 cents worth
I have taught CCW classes in several states for 25 years now. One of the things I stress to my students is every story (like this one) or the one you see on the news tonight or read in the paper, or whatever. Take a moment and ask yourself "what would I do" run those scenarios in your mind. That way when it comes up, you already know what you are going to do.
Your daughter needs to educate herself (or you need to do it for her) about carry laws in your state, use of deadly force laws in your state, and if your state has a castle doctrine law. Buy her a seat in a CCW class, I had many folks that didn't want the card, they just wanted the information.
If she is going to pack that ruger, it needs to be every time out the door, not just when she thinks she might need it. It also needs to be "close at hand" and in the same place when shes in the house. High stress situations, are not the time to be thinking "damn, where did I put it?"
Not to make her or you paranoid, but your best defense is situational awareness.
I live in the very rural, closest neighbor is half a mile away, my wife's city girl friends say to her "aren't you scared way out here, with your husband gone half the time, the neighbors wouldn't even hear you scream"
She tells them "If there's any screaming being done it'll be the bad guy doing it"
I like strong women.
I'll stop now, like I said my 2 cents worth, your mileage may vary.