I don't like the way the media is categorizing this crime either. "Kidnapping resulting in murder". To me it should be "First Degree Murder, with concomitant kidnapping". The murder took place first, kidnapping second. Regardless of what her motives are. And there is no doubt in my mind that this should be a death penalty case.
I think this is the federal charge. There has to be a way to assume federal jurisdiction and that is through the federal kidnapping statute. The states have jurisdiction over murders within their borders, but the federal government doesn't have such jurisdiction unless there is some nexus to them, like murder of a federal agent, kidnapping across state lines, etc. If the state prosecutes, undoubtedly it will be first degree.