Is she really my best friend?

I have known and absolutely loved my best friend of 13 years since I first knew her. We have been through everything together. But over the last couple of years she has and still does things that really makes me doubt our friendship like; compare her life to mines, assume that everything that happens to her is going to happen to me, and if it doesn't she appears to be disappointed. she wants to know every detail of my life, but intentionally hide things about herself. She assumes the negative about me and the positive about herself. If something good happens for me, she cuts the conversation short or she will somehow have to leave or get off the phone, but she will discuss her good news all day long and cut you off to talk about it. Whenever she finds a new boyfriend she disappears and changes until that relationship fails, then she contacts me after a year or more crying the blues and I am there for her, but each time she finds someone new, she cuts me off. If I find someone new she will call me more than ever and I mean everyday to want to know whats going on every minute. I don't cut her off, I still communicate with her as I normally do. As much as I value her as a frien of so many years, I have my doubts about the sincerety of our friendship on her behalf. Do you think she is my real friend or a foe? I have cut off so many people in my life including family because I have been betrayed a lot, but I have such a hard time when it comes to her. I wanna believe she is my real friend, but I also need to know for sure. What do you think, is this something that real friends do with no harm meant, or is this just not right. I have never had a really close friend other than her before, so I am confused about if I could be over reacting.