I would say that the most important thing would be to go and recognize her accomplishment. Really tell her how proud you are and what an achievement it really is to graduate. I graduated two years ago and that is what I wished for most; recognition for my accomplishment.
As far as gifts go I went online to findgift.com and they had some good ideas. There is a graduation bear that you can autograph. You could have your whole family sign it and give a little message it was only $6. Or the angel of learning by willow tree $12. You can find this at Deseret Book. I love and collect the willow tree figurines. Anyway, here are a few ideas and I will keep my thinking cap on.