Screw it, do what you want to. Like gitem said, tell her to pound sand, but be nice and strategic about it. You are staying with them. Tell her that you're not breaking any laws and they'll stay in the car, not in their house. Then offer to take her to the range and you'll teach her how to shoot, or at least watch, so that she can be a little educated about her phobia. I know, nobody wants to take someone like that to a range, her head might explode. But even if she declines to go, she'll know that you're on the level and you're not a mass murderer.
