To Richard: doesn't the fact that she woke up and went to the spa suggest that there weren't any signs of a crime scene in the room? If there was an obvious crime scene in the room or on the balcony with all the blood the Smith's claim was there, surely she would have noticed, right?
Also, perhaps there is a good reason for her going to the spa. I highly doubt that most people in that situation would wake up and immediately conclude that their spouse was either murdered or fallen overboard - that is probably the last thing I someone's mind. Perhaps Jennifer and George had really been looking forward to going to the spa, and perhaps Jennifer woke up and said to herself, "I can't believe George got so drunk that he passed out in another room. He is going to be so mad that he missed our massage appointments and he deserves it." That seems to make some sense to me.
Maybe things aren't as they seem and perhaps there are good explanations for what appears odd to you.
Also, I am not sure why you drag the Natalee Holloway case into this. They are completely un-related incidents.