Why she is angry to me?

i have a friend.. she a girl.. im a guy.. were teenagers.. were friends and we txt each other almost everyday..( i love her but im shy to say it) and one day i ask her that is it true that shes in a relationship with my friend.. and she said yes.. im sad but she tould me im very nice to her.. and im still happy even she and my friend is in a relationship that she told me im a very nice friend to her.. after chatting with her.. i played basketball (dont know about 2 hours).. after playing i go back to home and i saw i message on my cellphone she said (sorry not complete i forgot) '' dont txt me again huh.. you plastic face trying to be good'' im very sad that i cry because i dont know why did she text me with that.. i didnt do anything wrong.. (sorry for bad english im from pihllipines) i forgot to keep my cellphone and i ask my mother did she text anything to her..?? my mother said you dont have load how can i text (yeah shes right i dont have load i only chat on fb) could you answer me why she is angry with me.. dont know any idea.. plss help me love her so much <3 <3 ( i already accepted that she having a relationship with my friend but i couldnt understand why she texted me angry that i didnt do anything and im very nice to her because i love her)...!!