If Henry heard what Thorpe was saying, he has a right to be fully insulted by the boorish behavior. Thorpe is not just talking to Catherine; he is claiming she owes him the dance and not Henry.

Just one more example of Thorpe trying to get Catherine to break a commitment to the Tilneys to suit his own selfish whims.

“Heyday, Miss Morland!” said he. “What is the meaning of this? I thought you and I were to dance together.”

“I wonder you should think so, for you never asked me.”

“That is a good one, by Jove! I asked you as soon as I came into the room, and I was just going to ask you again, but when I turned round, you were gone! This is a cursed shabby trick! I only came for the sake of dancing with you, and I firmly believe you were engaged to me ever since Monday. Yes; I remember, I asked you while you were waiting in the lobby for your cloak. And here have I been telling all my acquaintance that I was going to dance with the prettiest girl in the room; and when they see you standing up with somebody else, they will quiz me famously.” (Ch. 10)