The woman was seen standing outside the Milk nightclub overseas, lighting up a cigarette.
A witness said a man came close to her and allegedly blew out her match, which annoyed her and led to her flicking her cigarette at him.
In response, the man punched her hard in the mouth, knocking her to the ground.
Pictures show the girl laying flat on her back as she appears to be unconscious.
Passerby then appears to help her up to her feet.
It is not clear if the incident was reported to police and the names of the people involved are not known.