Try and realize that you might not of been the best for her, and now that shes happy, you need to be happy to. Do things you like and keep your mind off of that relationship. DO NOT REBOUND it will make it worse and hurt someone else in the process. Just take a few months to yourself, someone will come along. If shes your friend on social networks delete her, delete her number so you cant see her. The sting will never go away until you find something else to fill the void.

Good Luck