Who is Calpurnia from Claudius the God and His Wife Messalina and what is their importance?

Calpurnia, a prostitute, is also Caludius' mistress before his marriage to Messalina. After his marriage, Claudius purchases a villa in Ostia for Calpurnia, where she retires with her friend, Cleopatra. When Claudius dedicates a granary, Calpurnia sends him a note warning him to take care, as there is great danger to him and to Rome. When Claudius visits her, it is Calpurnia who reveals the truth about Messalina and her affairs. After Claudius marries Agrippinilla, Calpurnia's home is mysteriously burned to the ground with her in it. It is made to look like an accident, but Claudius is well aware that it is his wife's work.