How to move on from a break up?

Hi! My girlfriend left me 6 months back and I was so affected by it that I went into depression. My parents send me off to Dehradun to live with my uncle. I joined some time pass course there and also made friends. I was slowly trying to get over her. I lived there for about 3 months and when I decided to come back to my home town, I saw my girlfriend with her friends in Dehradun. I followed her and traced the house where was putting up. I postponed my plan of going back and decided to stay for some more days. I found out that she is living with some relatives and those girls are her cousins and not friends.

To cut the long story short, I once again fell in love with her. We even bumped into each other in a market area where I was with my uncle. She greeted me and even touched my uncle's feet. I realized that she isn't angry with me. But she told me that she is getting married to a Dehradun based guy and that's why she is here.

Since that day, I can't get over her. I am going crazy. How do I get over her? I can't forget her.