Why won't Blanche allow herself to be seen in the light

cuz she'll burn up like ash

In A Streetcar Named Desire, Blanche is a woman who is extremely concerned with beauty. She wants to be considered attractive, and is also interested in finding a husband. However, as she is in her thirties, she believes that her beauty is diminishing. Blanche only allows people to see her in low light because she does not want people to notice her age. Moreover, she hopes that this approach will add an air of mystique to her presence.