My best friend and i recently stop talking and im not sure if it was the right reason?

My best friend and i recently stop talking and im not sure if it was the right reason it was due to me and her brother my xboyfriend getting in a agrument and it got pysical and i was going to have him get beat up and she bugged out she was going to jump me with her sister like it got crazy but at the same time she hates her brother they dont get along and she always told me she has my back when it came to her brother and things pretty we were best friends and now we dont talk and i dont get it i guess its true about blood is always thicker then water.