Hey,been there before,realised i couldn't let go but guess what, i did!!
and so can you!
The reason you are thinking of her is because you are pedestalling her,you think she is the best girl in the world,
she is better than everyone else and you want nothing else but her.
First:delete all reminding items you have of her,number,facebook-friend,anything and hide all pictures of her.Stop talking to her and ignore her if she talks to you.
Second: stop thinking like that,think about the negative things about her.(annoying laugh,kissed your best friend,very slutty,crooked nose,etc,etc but just anything bad about her).
Third:listen to songs that you like and think about the lyrics and the flow of the music,if they are songs that remind you of her,throw them into the listen-to-later music.eventually you can listen to that music and it wont remind you of her.
Fourth: talk to new girls,add them on facebook,friendster,what ever social-media site you are on
PLUS DELETE HER,make that your number one goal of today,when you sign on.
chat to a random girl on the street.talk to friends.Go on holidays with friends,get plastered and find yourself in the morning with a HB10 you scored last night
i hope this works for you,friend.
been in the same situation myself,but its easy to overcome.