A third possibility just occurred to me in the Sara-Kim-Eastman cheating snafu: be diplomatic about it. Tell her that I put someone else on it as backup, or even admit that she was the backup. It doesn't make me look bad, and it's true in a way. I mean, maybe that's not why I put her on it, but it is why I kept her on it after I knew Sara's was done, after all. And besides, it could have been true - this is a story it would have been a good idea to do that on.
This is both an ethics issue and a social skills issue: come on people, advice here please. Accept total and complete responsibility, expect the problem to fix itself (which is very possible, remember - it happens if she gets anything at all worth using), or tell a half-truth that makes two or even three of us look good and spares everyone's feelings?
Of course, by the time I get any advice on it circumstances will probably have forced my hand. So this is probably just another exercise in second-guessing myself and saying "coulda-shoulda-woulda". Oh well.
(A fourth possibility just occurred to me: tell Sara the confusion was Kim's fault. But I don't think even I am wimpy or dishonest enough for that.)