Of course, you realize that the time she did go took even Greta completely by surprise, right? Perhaps she really DID have a previous apointment, most likely to meet the incoming flight with friends from Alabama on it.
Was that what Mrs. H offered? She had another appointment? I just find it more than a little curious. How about: I can't stand the thought of being near the parents of the boy who knows where my Natalee is? But that's just me.