Quotes from Scene 1

BLANCHE: Now, then, let me look at you. But don't you look at me, Stella, no, no, no, not till later, not till I've bathed and rested! And turn that over-light off! Turn that off! I won't be looked at in this merciless glare!

This tells us that Blanche cares a lot about what Stella thinks of her and what Stella thinks of her appearance. When she cares about Stanley and Mitch thinking of her as being good looking we can assume that she wants them to be attracted to her or that she has experienced some attraction towards them. We know this is not the case with Stella as they are related. So this comes from  a place of insecurity and a need for validation from everyone around her regardless of who it is. This tells us that Blanche's self esteem is ruined.