How to ignore a "best friend" ? And is she really my best friend ?

We've been friends since the beginning, I've known her since birth basically. When we got in 5th grade she began to change, like she acted like a bossy preteen. She hated her mom. She dressed in short shorts that showed her butt-cheeks. She stuffed her bra. She acted rude. We're now in 8th and she's still the same exact way. But over the years I've been nothing but nice to her. I gave her hugs, told her I loved her, cared, went to the doctor with her, told her everything was okay when it wasn't, gave her advice, it's too long of a list. And she turns on me and re-pays me by being a b**** ?Well recently my mom and dad went on a over night trip and I had to stay the night at her house my mom wanted me to hang out with her more then she invites another friend over too. Yes, I like this other friend. So we went walking around the block her friend slaps her cause she said something mean, then my "bestie" slapped me. It left a red mark. Then we pulled an all-nighter and then all she did was talk to this other friend so I ended up falling asleep first cause no one talked to me. Then the next day we went swimming and the "bestie" kept dunking me. And we did races to see who was the fastest and she pushed me back. Then I didn't say anything the rest of the day. And then today she blocked me on facebook. ? How can I ignore this girl ? BTW: She always tells me I'm her #1 best friend, but I don't feel like it. So is she really my best friend ? Help ? I'm so confused.