My wife's views are very much like your girlfriend's. She was more "anti" until a couple of frightening and damaging encounters between her car and deer. She now is more understanding of the need to control animal populations when appropriate.
Ortega described the stages that a hunter goes through, from whack 'em and stack 'em to rarely taking an animal. My wife thinks I'm weird because I will kill a game animal for food or trophy without compunction, but I'll catch crickets in the house and release them outside. When the local population of raccoons got out of hand, I live-trapped them and relocated them miles away. I moved 16 of them before they quit coming to my deck and the bird feeders. Not a bleeding heart, I just didn't want to kill them and have to dispose of the carcasses. I couldn't have eaten that many coons in the rest of my life!
Killing is an emotional thing for a normally adjusted person, and as such breeds wildly differing and contradictory opinions. Bottom line, animals must die to support humanity. Our species is just one of many predatory ones on the planet that depend on prey species to provide food and other sustenance. I will readily kill to eat or correct an imbalance in nature caused by mankind, but these days I have no desire to hunt some animals just for the experience. Thirty years ago I would have hunted anything I had the chance to pursue.