I really miss my friend. How do I get her to like me again?

[Charlotte]

Hi, I'm 14 and I had a best friend in primary school. We knew each other since we were 4 and we became great friends in year 1. We formed a group of five in year 4 and our group grew to 7 in year 5. Me and her were always talking to each other, she was one of my best friends in the group. She was such a good friend to me, she was always there for me and we could talk about anything together. But we went to different secondary schools. We still met up in year 7 and year 8 and chatted on Facebook. But then she invited me and another girl from the friendship group round. Things just weren't the same anymore. After that, she started ignoring me for 6 months, not replying to me or returning my messages. She sent me a message out of the blue saying she was sorry that she hadnt replied and we met up again, but she forgot my birthday. We met up and then she started makin more excuses when I wanted to meet up. She was forever busy. Now she's ignoring me again. :"( I don't know what I have done. I think about our memories in primary school and I really, really miss her. Is there a way I can get our friendship back?
xxx