She felt this pleasant drift immediately and spun around, being afraid that she would see someone at the doorway.

spun 是动词 spin 的过去式，spin 本意是"旋转、转动"。 around 是副词，表示"周围、四周"，在这里与 spin 搭配表示"转身"的动作。 spun around 表示"迅速转身"的动作。