The waitress (the boyfriend has an affair with) will be wearing the a white shirt with some of the top buttons undone and a short black skirt. This will add sex appeal to the character and will fit in with the theory that blondes are the most attractive people, since the actress playing the waitress is blonde.
As for the performers, they'll be also be wearing casual clothing during the narrative sequences because they'll be making brief cameos. As for the performance sequences, they will be wearing white dresses and jewellery because they will be performing in front of a white background. In philosophical terms, the performer's clothing will represent that they might be angelic beings, since one of the performers is in the restaurant during the one of the narrative sequence and she disappears when a person walks past her. This also shows that the performers could also be fallen angels, since they are roaming around Earth in human form.