What does Mrs. Lincoln think that the ship from Abraham Lincolns dream represents?

His life was coming to an end. Where the boat signifies his life.

Explanation:

National Geographic reports Lincoln had another dream that seemed to foretell his assassination. On the night before his death, Lincoln supposedly dreamed that he was on a mysterious boat or ship. He characterized its purpose as "sailing toward a dark and indefinite shore."

According to the tale, just a few days before his assassination on April 14, 1865, Lincoln shared a recent dream with a small group that included his wife, Mary Todd, and Lamon. In it, he walked into the East Room of the White House to find a covered corpse guarded by soldiers and surrounded by a crowd of mourners.

Occurring near the end of the American Civil War, the assassination was part of a larger conspiracy intended by Booth to revive the Confederate cause by eliminating the three most important officials of the United States government.