It's relevant to ASND in that Blanche's self-image is one of glamour and prestige as she has lived through the aristocratic codes for all of her life. However, as you can see throughout the text, the times and sociocultural norms change and of course you begin to see the spread of the nuovo riche in the sense of the ending of the Post WW2 Great Depression. Blanche can no longer get by on just the grounds of being prestigious and living a great life due to her class status, as you see through her constant aversion of volunteering information about her great wealth tied in with Belle Reve (which is no longer existent). She lives a faux life in essence trying to live the way that she would have. She does this because of the way she sees herself; her self image.
I'm not too tip-top on my examples anymore but you shouldn't be analysing it like a text-response anyway.