You say, "I can see it is heart-breaking to realize the play meant more to Henry than she does," but I wonder if the play Lovers' Vows itself meant more to Henry, or if the play-acting he was doing within the context of the play was the more attractive. I can't really see Henry being that concerned with actually performing the play, but I totally believe that he is having a jolly old time toying with Maria's affections right under Rushworth's and Julia's noses. However, with Sir Thomas's return and subsequent kibosh on the performance, he realized that his golden opportunity for easily amusing himself at everyone else's expense was over.