This is one of the research methods to identify different aspects of an author's fictional story,(or) also used by HR managers in industries to compare employee characteristics and their job performance with each other.
Through measuring the similarity and contrasting the variations between specified components, the writer will examine components.
If im on the right track then a way to right it with dashes would be: Sacrificing her was a mistake-a mistake that could have been avoided. but i may not have understood the question??