In 1a what Claire did was morally wrong. Killing is considered wrong in deotological ethics, because it is treating an individual as a means by to an end (not potentially being murdered in this case).
1b. Only thing morally relevant is the murder. None of the rest matters.
2a. This one is not so cut and dry, because she killed the wrong twin, not to mention that had it been the mass murdering twin, there is no guarantee that she would have been attacked and murdered. She could have potentially been murdered, but she did not wait to find out if she was in danger. I would say that she is guilty of murder, because it was not out of self defense, but instead out of fear of a potential outcome. The ends did not justify the means, because she was in no danger, but instead acted out of fear.
2b. The consequences of the action are the only thing relevant here, because it was not the murderer that she killed. Had she killed the murderer, she would have a case for self-defense, and then the ends could have justified the means.