She pulled a Gaffney on us by making us think she had already left.

Gaffney 在这里指一种特定的欺骗手段或花招，可能源自人名或特定典故，表示"出其不意的欺骗行为"。 这种用法将专有名词Gaffney转化为普通名词，用来描述某种特定的欺骗方式，类似"pull a fast one"（耍花招）的表达。