She was no longer the girl （that she was ）before she went to the countryside.
关系代词that引导的是定语从句,她不再是那个去乡村之前的那个女孩子了.3Q 关系代词that做什么成分that=the girl 做 she was 的补语（也称表语）就等表这个字英语一般称补语，the girl 是补充说明主语she 的。50-60年代学俄语，苏联人称之为表语，一直沿用至今。补语视乎更好理解些。