My best friend and me!

I fought with my best friend.We are having a school play next day.So we decided to do a small orchestra with our classmate and my best freind and i were playing the Flute .But my best friend did't like the part we decised.So she was upset and yelled at our classmate.Well i was upset too because i was the orchestra leader and i prepare the parts that they have to play.I surly listend to my classmates ideas too.But my best friend said to was "whatever~I don't care"So i dicided the part during the weekend and it was very hard to me.But now she is yelling to me!What is this situation?!What did I did wrong?I tried to understand her very much but now i don't want to be a best friend with her!Because after the schokl was over she didn't said "Good By"to me...so i thought i would apologize to her in a wide mind.So i called to her many times!But she didn't answer ant of my phonecalls...I almost wanted to cry!!Well i hope i don't fight with her tommarrow!^^