Elinor doesn’t regret writing to her mother, for Willoughby’s behavior doesn’t change. Marianne is depressed and doesn’t take care of herself.
They go to a party. Willoughby is there. He bows but does not approach. He is talking to a young lady. Marianne is delighted to see him and is about to go up to him. Elinor holds her back, telling her to wait for him to acknowledge them first. When Marianne calls out to him, he comes up and addresses Elinor. Elinor is too unnerved to say anything.
Marianne is indignant. She asks why he is treating her like this. He shakes her hand reluctantly, flustered. He excuses himself and returns to the lady he had been talking to previously.
Marianne looks like she is going to faint. When she revives, she asks Elinor to retrieve him so he can explain himself. Elinor says it isn’t the time or place for explanations. Marianne is distraught. Elinor requests Lady Middleton’s permission to leave, explaining that Marianne is unwell.
Elinor realizes that Marianne had believed herself engaged to Willoughby, and he no longer wishes to uphold it. Only a change of regard could explain his behavior. Elinor is angry about his behavior, though he seemed embarrassed…which seems to indicate that he knew he was behaving wrong. She believes he did once care for Marianne.