I don't know if I'm crazy optimistic, but I'm going under the assumption that LE must have satisfied itself that KK did not participate in the murder or assist during or before the fact. That her crime, if properly prosecuted, would have been accessory after the fact and they knocked it down to witness tampering for her cooperation. Because if they knocked her down from a far worse charge, that would tell me they don't have much of a case.
Which, maybe they don't without a body. I don't know, I'm feeling squeamish about this one. I hope the information they are keeping close the vest is good information. It's hard enough to prosecute without a body as it is.