"I"m not young and vulnerable anymore," (book) is Blanche's response to Stanley's inquiring criticism of her previous marriage. This obvious untruth demonstrates Blanche's last grip on a deep struggle to save face. Another example of Blanche's denial is her conversation with Mitch about his own dead lover. .
Blanche: Sick people have such deep, sincere attachments.
Sorrow makes for sincerity, I think. Mitch: It sure brings it out in people. Blanche: The little there is belongs to people who have experienced some sorrow. (book).
I am unsure here as to whether Blanche is trying to justify her own behavior by blaming it on her unfortunate circumstances, or if she is truly unaware of the irony of her own statements and really does not realize that she is sick (although far from sincere). There were tons of other great quotes that demonstrate Blanche's denial and Williams also created countless blatant examples of this through Blanche's fear of light (because of its revealing nature) and her constant bathing.
After being intriguingly confused by Blanche's faulty disguise, the play works through several revelations that help to identify Blanche, who by this time is firmly planted on the path to destruction. "Stella: She is (delicate). She was. You didn't know Blanche as a girl. Nobody, nobody, was tender and trusting as she was. But people like you (Stanley) abused her, forced her to change." (play) Several references to the suicide of her young husband help pinpoint this as the catalyst to the chain of events where Blanche uncontrollably chose desire. Blanche takes her husband's sexual orientation as a personal insult, thinking that she was not "good" enough and hence in a way "made him gay," (although the homosexual reference in the play is pretty vague and totally non-existent in the movie, it fits as a crucial piece of information on why Blanche is the way she is). As previously mentioned, this chain of events becomes a rumbling locomotive hurtling towards Blanche's destruction.