I feel it's best to not move in with my girlfriend until she gets rid of her dog.
Is there a reason you don't like her dog?
I just don't like her dog.
Is there a way you can learn to tolerate the dog? People usually take care of a pet for the duration of it's life, and I'm sure she loves the dog deeply. If you give her this ultimatum you may find that she chooses the dog over you.
I will get over the dog.
I'm glad you're able to make the effort to try to get over the dog. Your girlfriend will really appreciate this and throughout time you may learn to love the dog.