Following her death, the spirit of Emilio's Wife remained on earth and unable to move on, due to unknown unresolved issues. During Dr. Zorba's travels around the world, he met and captured Emilio, his wife and her lover in Italy and imprisoned them in his mansion.
In the mansion, Emilio's Wife is shown several times to be kissing her lover, only for Emilio to then catch them and kill his wife with his meat cleaver; suggesting that the ghost of Emilio's wife is reliving the moment when Emilio caught her cheating on him over and over.
When Dr. Zorba was murdered and became the twelfth ghost, Cyrus Zorba and his family moved into the mansion. Emilio's Wife and the other eleven ghosts presumably crossed over when Benjamin Rush died and became the thirteenth ghost.