I went out with this girl for 2 years and now she left me. And she been close with this guy for six months and I think they are in love. What do I do?

You do what you should have done the moment you broke up. You go no contact and move on with your life, she didn't want you when she broke up with you, why would you think that she wants you now? It is time to move on my friend.

Leave her alone and get back to enjoying your own life.