Your girl's insistance on moving the relationship forward might stem from her unhappiness with the current state of the relationship. When was the last time you went out somewhere nice? When was the last time you did something spontaneous? When was the last time you took her away for a weekend outside of the metropolitan area? If you don't have good answers to these questions, start there.
It might seem like a strange contradiction to the commitment-phobic mind, but many people move relationships forward because they are unhappy with the current state of things. If your relationship has grown stale, nourish it before you put it to the test. Go spend the weekend at a bed and breakfast: It won't kill you and it is way cheaper than having your wedding three years too soon, not to mention the cost of divorce.