I doubt Ted Kennedy ever felt any real remorse over the ‘accident’. If he had any it was that he suffered humiliation because of it. As for Mary Jo, Mary Jo - Who???
There were a few scenes in the movie where Ted appeared to show remorse, but they quickly dissolved into contortions of self-pity and weakness. It’s hard to tell if he really felt any of it.
I heard he actually joked about it on occasion.