Blanche's confession of her past life is almost too much. It has that Tennessee Williams quality of sensationalism. It is almost unbelievable, and, as some critics would maintain, unnecessary for her to have such a lurid and degenerate past. Her confession doesn't seem to fit with this delicate moth-like creature on the edge of disintegration. But the opposite argument must be seen. Williams has attempted to show how Blanche's over-delicate and over-sensitive nature was the reason she sought escape from her failure with her young husband by turning to alcohol and to intimacies with strangers.
When Mitch accuses Blanche of lying to him, she maintains that she never lied "inside. I didn't lie in my heart." Blanche means that she has used some deception to trap Mitch, but a certain amount of illusion is a woman's charm, but as she said to Stanley in Scene 2: "when a thing is important, I tell the truth." And she did tell the truth to Mitch when she told him that she loved and needed him and that they needed each other.
Mitch, having learned of Blanche's past, then feels that she should sleep with him. In his disappointment with the truth about Blanche, he doesn't realize that she could give herself to a stranger but not freely to someone whom she knew as well as she knows Mitch and certainly not under such crude circumstances. Therefore, at the end of the scene, Blanche is at her lowest ebb of existence now that Stanley has given her a bus ticket back to Laurel and Mitch has deserted her.
