Well, that's the thing that puzzled me.  Agree there must be underlying mental illness for this to happen.  Which type is somewhat of a mystery.  All was not well with her even prior to this event, based upon what I have gleaned from the scanty newspaper coverage. There was something going on that led to her marriage breakup and there were some dish-throwing events or something like that.  My best hunch is that she may be Bipolar, and the combination of her marital discord, any job stress and the infatuation with the other astronaut (which clearly was of psychotic proportion), tipped her over the edge into this delusional episode.