No this story is phony. I am convinced that Kennedy made this story up to make people think he wasn't out drinking before the accident.
Maybe I've missed something, but didn't he just confess to drinking when he didn't have to (yes, a lot of people including myself believe that he must have), but this would make it impossible for his supporters to say that he wasn't drinking....what difference does it make whether it was at a bar or a lady friend's house?