The brother and sister pair Eleanor and Henry have both been aware of Catherine's infatuation/liking for Henry. I get the impression that Henry has been both amused and flattered by it. However, I believe the boofhead is to be credited for arousing pangs of jealousy in Henry. As early as the first week of Henry's return to Bath, he gets irritated by Thorpe intruding on his time of dancing with Catherine.

That gentleman would have put me out of patience, had he stayed with you half a minute longer. He has no business to withdraw the attention of my partner from me. Ch. 10
Moreover, Henry gets alarmed when Catherine says she feels obliged to talk to Thorpe if he interrupts again, and is only satisfied when she affirms that she does not want to talk to anybody else.