Proctor told Elizabeth that several people had been present when he spoke with Abigail in town. In truth, they were alone for some time.
The moment that the two of them were alone, Abigail attempts to persuade Proctor to rejoin the affair they had been carrying on. Proctor refuses.
Elizabeth does not have confidence in Protor's ability to refuse Abigail.
John’s previous indiscretions with Abby have not yet been forgiven, despite his attempts to make amends.
She doubts that, having been lied to once, she is being strung along once again and that Abigail and John will return to the affair.
Though Proctor expresses regret for the affair and swears that he is done with Abigail, Elizabeth has a hard time believing him. She wants Proctor to prove his change of heart and demands that he tell the court what Abigail had confessed to him when they were alone. Proctor refuses.
She is suspicious that this is because he has feelings for Abigail.
Proctor, at this point, feels there is nothing more he can do to assuage Elizabeth's doubts about his intentions and his feelings.