Sorry to hear that Emily let you down.
I've had this when the previous punter has decided to extend their booking (this wasn't with Emily) and was offered their ugly flatmate following extensive comms right up to the door. If this is what happened to you it's quite unacceptable. Clients need to be told sorry but no extension because of another booking. I know that WGs have a high percentage of no-shows for first-timers and that the money from the extension is guaranteed, but it really isn't good form and deserves a negative rating.