Dependent on my ex/best friend

I was with my ex for almost five years. We dated for one year, lived together for almost three, and were best friends the rest of the time. We would always do everything together and for the past almost five years I have spent most of my time with her, even at night sometimes we would spend it at each other's house. We would text throughout the day, talk on gmail while at work, and hang out every evening and on the weekends. From one day to the next she started dating someone and completely put me to the side. She would not want to hang out any more, stopped texting and would rarely want to talk. I felt like I was begging for her friendship (which I was). I was planning on asking her to get back with me again because I am still in love with her. This happened about a month and a half ago and I still miss her like crazy. I feel alone and lost without her and I wish things could go back to normal. When she said she needed space I felt like I was being abandoned and I realized how dependent I was on her. I realize it was unhealthy but I don't understand how she could put 5 years of our lives away for someone she just met, and I don't understand how she doesn't miss me like I do if most of the time she was the one that wanted to be with me. I don't know how to move on without her and in the back of my mind I still hope everyday that she will come back to me. I'm really sad.