I have been best friends with this girl for over three years. and she is the type of girl that gets pushed--?

around and gets put down by people. i admit that i am part of doing it and i was wronge. but i always asked her if there was anything she didnt like about me and she said nothing. we told each other everything. on the phone she would always say i hate being pushed around and being put down! and i would always say then stand up for yourself. so one day at school she told me that she didnt want friends puting her down so we werent talking for the past week after that. i finally called her to see if we were friends and she said not to even try. so i didnt talk to her after that either. at the end of the year i talked to her probably like two times. so i called her that night and asked if we were friends and she said it would be awkward to hang out with you and said that we have nothing in common and all that. she had changed so much then what i have thought. i really miss her and i really want to be best friends with her again. what should i do?? PLEASE HELP