In the mirror universe, Jadzia Dax (played by Terry Farrell) was a Trill soldier of fortune who worked for the Terran Rebellion. She was the lover of Benjamin Sisko, and after Sisko's death, the lover of Julian Bashir.
When it appeared that her lover had returned from the dead in mid-2371, Jadzia immediately greeted Sisko with a slap to the face for making her think he was dead, quickly followed by a kiss to show how glad she was that he was alive. She didn't realize at the time that the man she thought was her lover was in fact the Benjamin Sisko from "our" universe. (DS9: "Through the Looking Glass")
In 2372, when Sisko returned to the mirror universe, Dax immediately pulled a knife on him, warning him to never touch her again. Jadzia later joined her new lover, Bashir, on a mission to delay the Alliance's attack on the rebel-occupied Terok Nor. (DS9: "Shattered Mirror")