In the case who gets up is to blame ?

Hello, this morning the following happened to me. At a slightly driven junction (light turned off and no stop sign) I drove someone on the back. The driver stopped first at the stop line then continued to brake again at the line of sight then continued and then made 2 meters further a full braking although no car was in sight. I then drove her relatively slightly on the back. At her there is nothing to see with me the shock bar is damaged. e regulation who drives on the back is to blame or not ? no police were called. anii