How can Blanche's madness be shown using quotes?
Although we don't discover the true depths of Blanche's mental illness until later, the signs are certainly there early on in the play, as we see from the following words she speaks to Stella:
I want to be near you, got to be with somebody, I can’t be alone! Because - as you must have noticed - I’m – not very well… [Her voice drops and her look is frightened.] (Scene 1).
We sense that something's not quite right with Blanche. When she says she's not very well, we know that she's not referring to her physical well-being. Ironically, it's not her being alone that eventually leads to her being committed but spending time with other people.
And funerals are pretty compared to deaths. Funerals are quiet, but deaths – not always. (Scene 1).
Blanche has experienced a number of deaths in her unhappy life. She can handle funerals, but the deaths themselves have clearly had a deeply damaging effect upon her mental health. The aching fragility of Blanche's mind is in evidence here; she is simply too delicate to survive in such a harsh, unforgiving world.
There’s so much – so much confusion in the world… [He coughs diffidently.]Thank you for being so kind! I need kindness now. (Scene 3).
Blanche desperately needs someone to help her make it through each day in this confusing world, a world in which she does not really belong. For a brief hopeful period, she thinks that Mitch is the one to help her. Sadly, Blanche becomes as thoroughly disillusioned of Mitch as of everyone else. Once he's rejected her, then there's no one left to help, and so there's a frightening sense of inevitability about her subsequent descent into madness.
I don’t want realism. I want magic! [Mitch laughs] Yes, yes, magic! I try to give that to people. I misrepresent things to them. I don’t tell the truth, I tell what ought to be truth. And if that is sinful, then let me be damned for it! – Don’t turn the light on! (Scene 9).
As Blanche increasingly comes to feel that she cannot handle this world, she retreats deeper and deeper into a world of fantasy, of the imagination. Only there can she be safe. But, try as she might, she cannot fully escape the world nor its lurid, glaring light, the truth that exposes her sordid past for all to see. Blanche is painting herself into a corner, leaving madness as her only refuge, the only available source of comfort and repose.
You know what I shall die of? I shall die of eating an unwashed grape one day out on the ocean. I will die – with my hand in the hand of some nice-looking ship’s doctor, a very young one with a small blond mustache and a big silver watch. […] And I’ll be buried at sea sewn up in a clean white sack and dropped overboard – at noon – in the blaze of summer – and into an ocean as blue as my first lover’s eyes! (Scene 11).
Blanche has effectively given up her struggle with reality. In the face of all her troubles she's retreated completely into a world of fantasy and delusion. There's no going back for Blanche now; but then, she wouldn't want to return to the real world, in any case. It's only in madness that she can find any glimmer of hope. She's safe in her own little fantasy world, and it's a telling indictment of society and how it's treated her that the attractions of insanity are so much greater than those of the so-called real world.