No other author has ever interviewed Carolyn Bryant Donham, which took place 10 years ago when she was 72. She's still alive at 82, though in seclusion. The book doesn't say she specifically expresses regret for what happened, though she expresses great sympathy and tenderness for Till's mother and what happened to the boy, which the reporter notes comes across like close to the same thing.
The piece isn't very long and worth checking out. You can find it here.