How to forgot lovable girl

Hi all, I'm currently working as Software engineer. I loved one girl very sincerely during 4 years of my college days. But I didn't propose her for the first 3.5 years of my college life due to fear. and I had not much speak with her on that time. During our final year tour, I got a chance to speak with her because we are in the same bus. on that day,i was thinking like how to start to speak with her, but she suddenly smiled at me and speaked with me voluntarily. I really surprised. On that day we had lot of fun. One day she told to me like "you are looking so cute" with her pretty smile. Really i m not expecting this and i felt like i m the luckiest person n the world. I got a lot of chance to propose, but i wasted those chances. One day I proposed her.But she rejected my proposal and said like "you are not under expectation". after that i wanted her to tell me her expectations. but she is not ready to told that and after that she stopped to speak with me. I tried lot but no use. one she scolded me lot and told "dont follow me and waste your time". This is the last word for her to me. now 3 years over after this incident. but still i'm not able to forgot her. I wanted her the reason for rejecting me. but she is not ready to told me and avoiding me. its really hurts me lot. i dont know how to convince her or forgot her and concentrate on my job. now we are in different company. some of my friends are reminding her memories again like "I had seen your gf and she is looking cute now. and you want to she her". also they wantedly sending her photo, contact numbers to me. I'm not able to avoid this situation fully. we are 24 years old now. Can any one tell me the solution to how to forgot her and move on career or is there any possibillities for convince her?