Should I dump my girlfriend because she hates my dog?

Well... no wonder she's screaming at you. You're tormenting her. I'm sure you're scared of something - how would you feel if someone continuously taunted you for it? If she wants to get to know your dog, let her do it on her own terms. And if this whole situation bothers you so much, then break it off. But when you're purposely letting your dog up and scaring the crap out of your girlfriend - that's just immature.