Who is Bislcavret's Wife's Lover from The Lais of Marie de France and what is their importance?

The Bisclavret's Wife appears in Bisclavret. Bisclavret's wife no longer loves Bisclavret once she learns he is a werewolf and schemes to get rid of him. She conspires with a knight to trap Bisclavret in his werewolf form and then marry the knight. Her treachery is discovered by the king and she is banished after Bisclavret has attacked her and torn off her nose.