My long-time girlfriend humiliated me. Please help, what should I do now?

I met this girl in the year 2003 and it was love at first sight. We were going around well till 2007. We had the usual ups and downs, arguments etc, which every relationship has. But I didn’t realize that she was manipulative. She changed her job in 2006 and she also changed herself as a person. She was waiting for an opportunity to dump me and she finally did it as I argued with her when she denied coming out on one of the weekends. After a week when I tried to contact her, she called herself quits. She told that this relationship will not work out. I assumed that she is upset with me coz my straight forward attitude is very often is-interpreted as being rude. I waited for some more time, pleaded guilty, cried and begged to come back. She didn’t. She was very adamant. Over the period of time, I didn’t disturb her. Even, she changed her mobile number and email IDs. All this happened in 2007. In the year 2008, I searched for her profile in Face Book and was shocked to see her pictures with another guy. I was devastated…! I sent her many messages in FB and her new email ID, no response. Recently, I got her new mobile number from one of her friends. I sent her a text message asking her if she ever, even for minute, felt guilty for cheating and dumping me. She replied very sarcastically stating that she didn’t felt guilty and started abusing me not to send her any message and even told me that I need psychiatric attention. Over all these years, I was not able to get over her feelings and I didn’t even attempt to fall in another relationship. I was in a wrong assumption that she will come back to me one fine day. I very often dreamt of us both patching up. Never in this period I have abused her, didn’t I raise my voice when I sent her emails. I was very polite and humble. I was very honest and sincere and was trying to win her back. I was unsuccessfully trying to win her back from 3 years. She could have broken with me smoothly, but yesterday she turned the whole incident uglier. She could have met in person and spoke to me about the incompatibility and moved on. But from the day she broke-up with me, she didn’t give me a proper reason or explanation. I thought she will come back to me one fine day and was waiting for the day. From Dec-13-2003 till date, she was in my thoughts every minute. I have each and every SMS, emails, letters received from her from 2003 saved in my computer. I loved her. I thought that people will change over a period of time and mellow down as they grow up. But she got very irate and irritated when she got my text message and was shouting at me. I felt very humiliated and it hurt my self-esteem very hard. I am very disturbed. The more I was humble and polite, she shouted at me in high voice. Never in this whole argument had I used profanity. I finally got to know that she will never change. What should I do now? Should I give it back to her strongly or stay calm and move on?