How about some time with just the two of you doing some of her favorite things - a day looking at art, listening to beautiful music on the beach, a weekend some place that has special meaning for the two of you or a new place for new memories.
I am sure she has given you hints knowing that Christmas is coming. When you're shopping with her, observe what attracts her. If she likes to wear jewelry, get one that's designed to fit her personality. A holiday or a romantic dinner in a very elegant restaurant.