why should I not b tha bigger person?

my xbest friend (ill call her A) and I recently ended our friendship. but let me tell you the story. we were friends ever since 3rd grade and nothing could tear us apart but in 6th grade my other xfriend (ill call her B) came as the “new girl” so showing a little hospitality I helped her fit in. in 7th grade me and A were still close but we were starting to accept B finally. in 8th grade me A & B were all close as close culd be. but in the middle of 9th grade A & B got really close and started leaving me out of events and things. we resolved the problem by time school was out. but I moved not far we still went to the same school and it seemed like since I moved and I had to get familiar with the people around me they started disliking me. now in 10th grade they don’t talk to me anymore all because of a dumb he sed she sed crap that was sed.(during 9th grade summer I was in other states the whole summer and it was said that I was at home talking bad about them) so I tried to handle it in the beginning of 10th grade but A said she doesnt want to associate with me because I changed and not for the better because boys started talking to me and always trying to hook up with me. but now I c A everyday at the lockers {shes 2 down from me} and I want to say something but B is always with her and B has a smart mouth and shell sai something smart and A is gonna do the same thing and not take me seriously… PLEASE HELP I WANNA TALK TO HER AGAIN AND I don’t know WAHT TO DO