After the Dominion attack on the Maquis in 2373, she retreated with many other Maquis members to Athos IV. She then sent a message to Eddington directly claiming the Maquis had launched several missiles towards Cardassia Prime. It was really intended to be intercepted by Klingon forces in the area, and was really a signal that she and others were all right and made it to Athos IV. Furthermore, she expected the message to be brought to Eddington in prison and he could then pretend to disarm the missiles while he could make it to her.
However, a joint Cardassian/Dominion effort virtually destroyed the Maquis on Athos IV. Sullivan was among the few survivors. She was relieved to be rescued by Eddington and Sisko, who indeed took her message to him. A Jem'Hadar sneak attack followed the arrival of the two men and Eddington gave his life to ensure his wife and Sisko survived. (DS9: "Blaze of Glory")