Sentence:  “Oh?” she said. “So you have decided to revise my guest list for me? You have the nerve, the – the –” I saw she needed helping out. “<WSD>Audacity</WSD>,” I said, throwing her the line. “The <WSD>audacity</WSD> to dictate to me who I shall have in my house.” It should have been “whom”, but I let it go. “You have the –” “Crust.” “– the immortal rind,” she amended, and I had to admit it was stronger, “to tell me whom” – she got it right that time – “I may entertain at Brinkley Court and who” – wrong again – “I may not.” 
Meaning of the word marked with <WSD> tags:  Insolent boldness, especially when imprudent or unconventional.