When my father was young he had a pet bird. One day a window was left open, a cat snuck in and ate my dads pet. He was devastated and has hated cats since. The cat was only being a cat, but it's understandable why my dad would never allow me to have a pet cat. He could not be near a cat without hating it and I guess holding it personally responsible. My point is, perhaps your girlfriend has her reasons and would be willing to work on it if you talked openly and honestly. She needs to respect your opinions and you need to respect hers if things are going to work. Good luck.