You are mixing apples and oranges. There is no indication that, despite the fact she was spending nights (and weekends) with the boyfriend, the ex would not be going. We don't know anything about what the cruise plans were. When Crystal and he last talked about them. Or really anything about it.
If you read the conversation with BB she was saying that the ex did not know yet and wouldn't know since she blocked him on FB (BB referred to the ex being able to learn about it on FB) and the entire conversation was about whether to tell him or not. What was with all the deception in keeping from the ex? Why hide it at all? It was going to have to come out sooner or later so why not just get it over with?
See, I see this case as pretty simple. If Crystal made it to the house then the ex killed her - plain and simple. There isn't any complication. But as of now the Sheriff Department has said that they don't have evidence of a crime yet. Their experience tells them that foul play is likely. Even as late as yesterday they haven't rule out whether she took off or not no matter how unlikely they think that is based on experience.
