before后面接定语从句的问题，一个美籍Youtuber说的一句话是不是正确

原句如下：

So obviously that girl hadnt seen learnt spelt with a t before which is Okay in British English.

请问这里的which是什么使用方法？ 我的剖析如下：假如before是连词，which is Okay in British English应该改为that is Okay in British English.

假如before是介词的话，which is Okay in British English应该是一个名词，which引导的句子可以看错名词，还请老师解答，万分感谢！

你为何没想到before是个副词，修饰hadnt seen呢？which引导非限制性定语从句，先行词为learnt spelt with a t。

你断句错误，致使理解错误。