Tell her you love her, that she is the best thing that ever happened to you. Tell her you cannot imagine living without her. Waking up in the morning, and seeing her face besides you is the greatest joy of the day and the greatest present she could ever give you. Tell her that if it weren't for her, you life wouldnt be complete.
And mean it! Cause we can tell when you don't.
Good luck, and congrats on you anniversary.