What just happened??

What a strange day it was.I suddenly made my friend sad...Before i go on with the story,let me tell you something about myself...

I am a chinese orchestra drum player.By last year october i started learning a new instrument called 'yang qin' or chinese dulcimer(if u haf no idea how it looks like,kindly search the web).The reason i started learning this instrument because my friend,Gwen(fake name used) influented me in learning it.And the main character of this blog is her-Gwen.

Gwen is the best friend/teacher(she graduated last year and now work as a temporary clerk in school)/percussion group leader of mine.Me and another friend of mine always protected her as if she's our sister.Three of us are best pals ever.

Just this afternoon,when we were having our weekly practice in chinses orchestra, there was an empty seat in the yang qin section,since i have no instruments during that song,i beg Gwen to let me play the yang qin.She forbids me and then i called her 'bat po'(of course i was only playing with her),but she just turn her face to the other direction and stopped facing me..this is when i knew that something is wrong. But after i learnt to play yang qin,i always do this to her(except for calling her bat po).I was totally worried,so i send smses to apologize.

In her message,she told me that she's not mad at me because i called her bat po,it's just she's sad because her friend(me) changed.Those words struck me.What just happened? I don't know.But about the changing,that confuses me. When did i change?How did i change? How should i make her not mad at me again??AHH!!!Anyone please help me!!