I remember that day. I had the honor of being one of the veterans who stood beside her on stage the day she originally said it.
She really never needed to apologize, since the media never broadcast or quoted her original statement. It was the truth of those words, Lincoln's or not, that terrified the media that day.
Whether Lincoln said it or not, and it can't be proven either way, his actions as President bear out his belief in those words, with only the possible exception of the hanging part.
I'm glad he did, and that it will now be part of the congressional record.