Stella Kowalski is Stanley Kowaslki's wife and Blanche Dubois' older sister. She grew up at Belle Reve with Blanche and moved to Elysian Fields in New Orleans when she married. Even though she is not the protagonist, Stella has an important role in the play.
Stella comes from a wealthy background but abandoned her past when she married Stanley and became part of the working class of New Orleans. We don't know much about her physical appearance, but we are told in scene one that she is about twenty-five and is gentle. Evidence in the book suggests that she was once very similar to Blanche, but chose to leave that world in order to escape the fate of her ancestors, who have all had "epic fornications". She abandoned her family leaving Blanche to deal with all the deaths of the family.
Blanche symbolizes a wealthy woman trapped in a world of illusion and Stanley is on the other end of the spectrum, being a working class animal-like man who craves to discover every truth.
Stella seems to be in the middle of that spectrum and therefore acts as a mediator between the two. She has Blanche's refinement and Stanley's understanding of the real world. Stella lied to Blanche about the size and comfort of her home and therefore did not want her to know about her new social situation. With Blanche's presence, Stella acts differently and tries to show her sister she has remained refined and cultured. Stella is easily influenced and very quiet. Blanche tries to be a mother figure toward Stella from the very beginning of the play. In scene one Blanche says : "I said stand up! You messy child, you, you've split something on that pretty white lace collar!" and then goes on criticizing her...