The Strange Young Woman, is a leader of a group of female cultists who are seen leading a ritual before the group enter the forbidden section. It is not revealed if she is a supernatural apparition or knows something the group doesn't.
She is shown pushing Benji to his death, holding a baby. This could imply that she and the baby represent some guilt of his past. However, this theory does not quite fit in with the cult scene. One alternate, and very loose possible explanation, is that she is somehow Marie Antoinette. This is hinted at by the inscription on the wall that is seen where Benji is sitting, AD1793, which is the year that Marie was executed. Marie also had a child named Sophie who died before her first birthday, possibly explaining the child in her arms. Once again, this theory does not well explain the cult scene, nor does it explain why she would be targeting Benji, or what she would be doing at the club. Whatever the explanation, she seems to have an especially strong connection to Benji, apparently paying him special attention at the club, and leading the singing that seems to affect him deeply, driving him into a panic.