My bestfriend left me for her new boyfriend?

i was bestfriends for 3 years with her ... we did everything together i loved her so much. and i still do... she taught me what was right and what was wrong ... we wer together nearly everyday. i knew this day would come. i just didnt know it would hurt so much... she left me for this boy that she was obsessed with for about a year ... she finaly got him and i guess spent to much time with him and forgot about me... but this has been going on for about 3 months or so ..and she hasnt called me and i havent seen her in 3 months.. shes like best friends with him now .. but it didnt bother me all this time... it only kicked in now .i dont understand... why would she leave me? i loved her so much as a friend :(