From her expression, I deduced that she didn't like the proposal much.

deduced 是动词 deduce 的过去式。deduce 由前缀 de-（表示"向下、彻底"）和词根 duce（来自拉丁语 ducere，意为"引导"）组成，字面意思是"向下引导"，引申为"通过推理得出结论"的意思。deduced 在这里表示"通过观察和分析得出某种结论"的推理过程。