The girl to whom I spoke is my cousin.哪个是主语哪个是从句?我老觉得子句子怪怪的,

The girl to whom I spoke 是主语,is 系动词作谓语,my cousin 作宾语.
主语中to whom I spoke 是从句,修饰the girl.
在从语中,可以理解为whom I spoke to,whom是宾格,spoke to 表示对谁说话,此处是将介词to提前.