My girlfriend's family strongly disagreed with us because of fortune telling.

Fortune telling is a superstition. As long as two people have true love, why care what the fortune teller says? If you change to a fortune teller, it may be another answer. Believe in yourself. Life is created by two people, not by fortune telling. Believe the facts, and the rest is just speculation. As long as you persist and make up your mind, your family will be moved. Let's go