get in有抵达、到达、当选的意思,这里不是别人爬到了头上的意思.头发在古代文化中有着三千烦恼丝的意境,而这里也是同样的，用get in sb's hair表示烦扰到某人、让某人厌烦.

【例句】
Marry was trying to prepare dinner,but her children were getting in her hair.
玛丽正在准备晚餐，但孩子们老是烦她。

Why are you were getting in my hair.
你为什么总来烦我。