这是定语从句中关系词作介词宾语的现象,在原句中which 做的是from 的宾语.
先把原句拆成主句和从句,就会变成：
1.she had run back in the direction.
2.from which she had come.再把from which 放到适当的位置上就会改成：she had come from which.而关系代词which指代的就是前面先行词 the direction,于是第二句话就会改成she had come from the direction .了.这样答案就一目了然了.