Question

she is the girl __you are looking for? 用who 还是 that？ 两者用法有什么区别

Answer 1

这句中who & that 都是可以滴……

在定语从句中~

只能用that的是~

（1）当先行词为all, much, little, none及由any, every, some, no所构成的复合不定代词时。
We should do all that we can do

（2）当先行词被any, few, little, no, all, much, some等词修饰时。
There is little work that is fit for you. 几乎没有适合你的工作。

（3）当先行词为序数词或被序数词所修饰时。

（4）当先行词为形容词最高级或被形容词最高级修饰时。
The best that I could do was to apologize. 我唯一能做的就是赔礼道歉了。

（5）当先行词被the very, the only, the last, the just, the same等修饰时。

总的来说that的适用范围更广啦~

但是 介词＋关系代词结构中，关系代词必须用which。
The house in which we live is very large. 我们住的房子非常大。

希望帮到楼主~

Answer 2

2者都可以
that可以指人或物
who只是指人

Answer 3

that 此处缺宾语 可以用that或者whom