请问为什么she's next door没有加介词in呢

请问为什么she's next door没有加介词in呢 she is next door 为什么不加in 文中一句话：She's next door,请问door前面不需要加the吗? She's next door 这里的she's 是不是she is?She is next door? she‘s the girl next door,Nice,but not in a heart that’s pure she is next door. she lives next door. 【she is next door】为什么是she is? she's next door 中next door 做什么成分 是什么词性 英语He met her and She met him.中的动词met为什么没有加S呢? she's next door的表语是什么性质 为什么on next day off可以加介词on,而next week却不能加呢(⊙o⊙)?