I had a dream about my grandma who passed away about 5 years ago. In my dream she was passed away too. In the dream I has found a book and in the last section of the book it was a little note to me and it said something like "congrats on your graduation and I'll be at your wedding". She had died my senior year of high school and I'm getting married in 7 months. We were always very close. What do you think this could mean? I cant get this dream out of my head.

It could be as simple as you wishing, while you're asleep, that your grandma could say those things to you and, because she can't in waking life, you're living out the nice image in your dreams.