Dogs should always ride in the passenger footwell if you ask me... it's safer for everyone. They are clear of airbags (if fitted) and they are neatly contained in the event of a front or side collision. Of course a rear end crash is the main problem but at least the dog will be stopped by the passenger seat and is on the opposite side of the car to the driver.
Bad luck about your car, your dog and your injurys... Good luck about you and your girlfriend being alive to talk about the ordeal.