Spritz was a member of a primitive culture who was taken from her planet by Jenkins, member of the Rulers of the Universe. Assuming she would be considered guilty by his murder, she disguised herself as a robot waitress. She was later framed for the murder, but River Song made the Rulers believe she was dead. However, Spritz had been set free by River to flee and see the universe. (AUDIO: I Went to a Marvellous Party)
Later references
While hiding her true identity from the Eighth Doctor, River Song adopted her name. (AUDIO: The Rulers of the Universe)