Catherine doesn’t appear to be hurt at all that Robert forgot her birthday. Perhaps it’s because he has just given her lots of other proof that he cares for and loves her—he has told her he supports her decision to go back to school, and he has expressed his confidence in her abilities. The tension that was present earlier in the scene has vanished. Meanwhile, there’s a moment of expectation between Hal and Catherine—it is likely that she is hoping that he will show romantic interest in her by agreeing to join them for her birthday celebration. The implication is that there may have been some sexual tension between the two, but that when Hal has his chance to prove his dedication to getting to know her by joining her for dinner, he declines and, by declining, makes Catherine reconsider whether he really was interested. After Catherine and Hal exit, Robert opens the journal and begins writing the entry that Hal shows Catherine in the first act. It’s the entry that proves that Catherine’s selfless caretaking was the right thing to do—he credits her in-home help for his remission.