Is she the real decision maker?

她正在作出决定吗？

Ultimately, he was the decision maker.

最终，他才是决策者。

Who is the decision maker for the project?

谁是项目决策人？

Who is the decision maker of this meeting?

请问这次会议组织这是哪位?。

The question is, "Are you a good decision maker?"

问题是，“你是一个好的决策者嘛？”