Somehow, a few more days passed and the female ghost supposed to haunt Zhao Ai appeared while Zhan Rong and Gu Mochou were away from the city. The ghost lady managed to stir some troubles before getting wiped away by Fan Zheng who had sought the help of somebody from the sect.
Actually, the ones to take care of the ghost lady with Fan Zheng should have been the group of three disciples from before. But they died, so the plot autocorrected it and made one of their seniors come in their stead. Things became more logical that way.
The ghost was tracked down because the one following her was much more formidable than the disciples. As a result, Gu Mochou's effort in saving the strong female ghost was wasted.