Six months ago, 19-year-old Xie Lei said goodbye to her family and friends and boarded a plane for London.

ago 是副词，表示“以前、之前”，通常与时间段搭配使用，如 six months ago 意思是“六个月前”。它用于描述从当前时刻向前倒推的时间距离，常与一般过去时连用。