I praise the response from wordprof., very well thought out. One's morality and justification can be different from person to person. In the  United States jury's decide these important questions. I personally think that the female in your excerpt was morally justified in her actions, but of course other's will disagree.

I agree with the above poster that it is important to distinguish between the legal issues and the moral issues.

Depending on the case and the location, the law has different terms and degrees of charges (and severity of punishment) for the taking of another life. Legally it is up to the judge and jury to review the relevant law(s) and decide how the particular facts of the case apply to the law. Legally there are definitely cases where the taking of life is justifiable.

Morally this has to be a personal question. Each of us has values that determine how we feel about situations like this. Poster #2 is a great example, as it is obvious that her morals and values make the taking of another life unacceptable in any situation. However I think you would find an equal number of people who would find that there are situations in which the taking of a life is justifiable (like the example you cited from the book). Morally this question can only be answered individually and even then it is not an easy answer. 

Two words need some exploration here.  First "murder" is a legal term--not every taking of a human life is murder.  Secondly, morality is not a legal term; it is a human judgment of right or wrong action based on a set of principles that can be religion-based or personal-philosophy based.  Loraaa's answer above has no validity as a logical argument.  We also must look at what is meant by "justified," another term calling for human, not legal, judgment.  While it may well be true that we all "agree" that cold-blooded killing for gain is morally unjustified, we cannot argue the point logically, only emotionally and personally.  As for the case you cite, morality is beside the point--we all act for our own self-preservation; that cannot be disputed.  Whether this was her only or best available solution, it is not our decision.  We can speculate on how we would act, but it is only fiction for us--it was real for her.  As for real-life cases like this, they abound, and juries make the decision as to whether it was "justified" homicide or murder.