Personally, I think that Marion's lack of morality lies (lays) in the fact that she was willing to sleep with the Sheriff despite her love for Robin. To my way of thinking, she has violated their trust, even if she has no feelings for the Sheriff. It's like the argument posed in that movie with Demi Moore and Robert Redford for a few years back: is it OK to sleep with someone for a million dollars as long as you don't "mean it"? Of course Robin's reaction makes him even less "morally correct" than Marion in the end.

Flatlander