How can i get my Girlfriend back?

So i went out with a girl for 3 and half months, had a great time, etc. liked alot of the same things all of that stuff. But later on we broke up and shes been going out with this guy for about 4 months and i miss her and want her back. any ideas? i recently came upon notes we used to write eachother in the school yr, also "our song" is fall for you by 2ndhand serenade. i was thinking give her the notes back with a cd of me singing / playing the song on my guitar.