Well that scenario was just to explain the "sayonara" part. I agree that she was likely knocked out and put in. Likely the trigger was placed as she was going out or on a timer. Otherwise what reason would she have for saying that? Since we know its not suicide, she needed a reason to say that at that time. Unless you think she was saying good-bye as to call off the marriage being the original intent. Which would again point to the fiance. Doing so would make it too easy (though, knowing Gosho, that would be the most likely). There is also the possibility that all that is a red herring to throw us off. It wouldn't be the first time Gosho has done that.
I currently have a few theories, but I can't confirm anything until we have more background information from the suspects.
For the record, I don't believe Bourbon is involved with this murder.
And, yeah Chek, there is that, but for some reason I get the feeling there was more to that than it being one of their people. I get the feeling that Vermouth is playing with a loaded deck if you will. So while that may be part of it... I get the feeling there is more to it.
@Martell, the fact the phone was there might be why she was awoken. In fact, if it was a bomb (or other detonation device connected to a fuel), her phone could have been linked to the satnav system, which was connected to the detonation device. In doing so calling her would activate the timer, while giving her time to talk and confirm the murderer's alibi. It would also serve to destroy any evidence of setting that system up, because there would be no way to link the number to the detonation device. They could only determine that a remote detonator was used. If done right, the evidence would be almost completely destroyed. Also, it would cast doubt on other people, allowing the murderer to escape without suspicion, because the person who called her, the fiance, would be the primary suspect.