It turned out she was the one who solved the mystery.

turned 是动词 turn 的过去式，turn 本意是"转动、转变"。 out 是副词，表示"向外、完全地"。 turned out 是一个短语动词，意思是"结果是、最终证明是"，表示事情的发展或真相出乎意料。