The literal meaning is a weapon of war such as a tank and/or the military resources of a country as a whole. In your example, however, the term is used as a metaphor or symbol of a mood and/or action associated with an event. An organization or person, for example, could use the term "we've gotta keep this war machine going." This reference might then refer to the duty of organized conventional and unconventional action for a cause. If I were to say to a person from a powerful country: "I don't want your war machine" then I could be using the term to refer to the ideology of that country in a way that means more than just their military might. If a person walks out of a situation "like a war machine" then that person's response was very impassioned in words and actions.

It seems clear that, in this context, the author means that she was very angry. However, we do not use this expression in this context in English. We only use "war machine," in a very literal way. For example: "The Wehrmacht was a war machine that fought at lightning pace." (The Wehrmacht was the name for the Germany army in World War II) In this context 'war machine, would mean that they fought wars very efficiently.