What to do when your best friend ignores you suddenly?

We been friends for over 10 years. Although she is generally a cynical and pessimistic person, she was always there for me when I need a shoulder to lean on. Problem is that in the past year, things have been going very well for me and not so much for her. I think she started to resent me for all my success in my personal life and my career (I never rubbed it in her face). We got into an argument back in the summer because she lashed out at me and told me hurtful things. We didn’t talk for a couple of months. I then moved to NYC for a cool work contract and she congratulated me but it almost sounded bitter. When I got back in town, I called her to check up on her and she’s been ignoring me completely. I tried emailing her, calling her but nada. It really hurts me that she would let me down like that. My bf told me she was never a true friend and to just let it go and focus on my new friends. How can I move on?