People who tend towards liberalism often cannot think of the possible consequences from their position. You just tell her that the only way to defend yourself against bad people is with a gun and leave. SHe won’t be receptive because she’s never been the victim of somebody who wants to harm her.
give her an object lesson on the realities of life. drop her off at one end of the hood and tell her you’ll pick her up at the other end in one hour. then don’t show up for two.