It's sounds like a great idea, but she is just a girlfriend. It's your lifestyle, live it how you see fit. I just want to warn you that if you get in a fight tonight, she can lock you out and you have no say.
This is not a high budget project so the potential financial loss is not an issue.
Not having all my guns secure is not good.
Not having all my guns not handy is not good.
Having guns lying around my parents house 40 miles away is not good. (especially since they are not around a lot)(they don't shoot)
Not being able to shoot when I want because I don't have something is not good.
So I find more pluses with this than negatives.
And we have been with each other for a while, this is not a fling that I'm mooching on.