If AU Dukat could make himself visible and heard, he would tell her that. But he'd also warn her that the fact that he died young (tragically
young by a Cardassian standards...even Tolkar seems like he may have more "free" years than AU Dukat had years in his life) does not mean that's her destiny, or should be her destiny.
I'm glad these are good tears, though, and hopefully she won't kill herself. Even when a person has sins and needs to make amends--that is oh so NOT the way to handle it.