Want to break up with a friend?

I know this friend of mine from the last 3 years. She has been my very close friend from the last 3 years. We have actually been more than friends. Sometimes gone physical also. But I never expressed my love for her fearing that I may loose as a friend and also that we cant take our relationship to the next level. Recently she has been telling me that she has got another guy and I am sure that they have a healthy relationship going on. She even today talks to me but off late I feel that she gets irritated too much with me and I dont feel that there is anything left in our friendship. I want to break our friendship even though I will miss her a lot as I love her a lot. Please let me know as to how can I break our friendship.