Why does Le Brun stay for the going away party?

Le Brun intends to leave when he gets paid before the party. Sylvie asks what it will take to get him to stay for the party. He says that he will stay for the party if Thisbe goes to the party. Sylvie says that is impossible, and he tells her he will be on his way after he sees Lucien for his payment. Sylvie gives in and tells him that Thisbe will attend, but she does not tell him that Sylvie will attend as a servant.