The glaring contrast and fierce struggle between the two worlds of Stanley Kowalski and Blanche DuBois are the main themes of Williams' play. These two worlds are so diametrically opposed that they can never meet. Thus, in order to bring these two together — to have these two encounter each other — Williams has created Stella. By simply having her married to Stanley and by having her be Blanche's sister, Williams then creates the perfect opportunity of bringing these two opposing worlds together under one roof.
Stella DuBois Kowalski is, then, a vital part in the struggle between these two worlds, and she is also the bridge between these two worlds. Both Blanche and Stanley are guilty of trying to involve Stella in their quarrel. Both attempt to win Stella over as an ally. Stella is the battlefield for those two warring factions, and both try to use her to accomplish their own ends. But Stella also seems to be the only answer to peace, for she is the only bridge between these two apparent opposites. She comes from Blanche's refined, educated, and sensitive world. She has, therefore, attained a mixture either consciously or unconsciously.
It is apparent that Stella is a battleground for the DuBois-Kowalski feud. Blanche continually tries to turn Stella away from Stanley, by belittling him every chance she has. She tries to prevent her sister from returning to her husband after Stella had been beaten by Stanley during the card game. Blanche does not try to hide her opinion of Stanley when she decides to tell Stella of her true feelings for her brother-in-law. She calls Stanley "common," "bestial," and "sub-human." Stella seems to become the tangible symbol of victory between the two warring parties. Blanche does her best in trying to grasp this symbol for herself. Blanche's influence is definitely weighty. The argument between Stanley and his wife in Scene 3 is directly caused by Blanche's insistence on playing the radio. Stella shows strong signs of her sister's influence. She even seems to repeat exactly what Blanche would say, "drunk — drunk — animal thing, you!" In another instance, she says, "Mr. Kowalski is too busy making a pig of himself to think of anything else!" These are words that most likely would come from Blanche's own mouth and Stella would never have uttered them before Blanche's arrival. Thus, Blanche has had some influence upon Stella.
But Blanche is not alone in her hopes to win over Stella, for Stanley is also guilty of trying to mold his wife's mind. He is continually trying to convince Stella that they had a better life together before her sister's arrival. He wants Stella to ask her sister to leave, and he continues his efforts in doing this. He does not need Stella's consent to throw Blanche out of his house but he, nevertheless, strives to get his wife's approval. Stella is reminded of the "colored lights" of their sex life together and of the happiness they once shared. He delights in telling Stella of her sister's immorality, hoping that this too will turn his wife against Blanche. Stanley tells her that it will be all right once again between them as soon as Blanche leaves.
But Stella's function is not just to be an object in this struggle, to be merely swayed from one side to the other. She also seems to be the only hope of a compromise between these two different backgrounds. As Blanche and Stanley represent two diametrically opposed worlds, so Stella represents a bridge between the two poles. For Stella shows that a meeting point of coexistence is possible between Blanche's and Stanley's separate worlds. Stella still has many qualities of Belle Reve. She has not allowed a gentle and refined nature to completely disappear simply because she has accepted Stanley and all he stands for. Nor has she allowed her upbringing to stand in the way of enjoying life with her raw and lusty husband. She has, rather, combined both worlds into one and has shown that these two apparent opposites are, if not compatible, at least co-existable. The problem between the play's two main characters seems not to be the irreconcilable worlds which they represent, but the rigid inflexibility of Stanley and Blanche in their respective attitudes. Stella seems to indicate that such a reconciliation is possible. She is not a perfect blend; however, she does show that a mixture of the two viewpoints can be workable.
But one should not maintain the position that Stella is a strong character. She is far from this. Blanche appears to be the weaker of the two sisters but this is a false impression. If Stella were a strong character with a definite mind of her own, a three-way conflict and not a two-way conflict would appear in the play. Stella would have a definite standard of action and would pursue this throughout the course of the play. But her definite vacillation between the two opposite poles of Blanche and Stanley is only possible because of her weakness. This quality in her character enables her to become a pawn in the death struggle between the two major characters. This weakness alone makes her a battleground. Stella does not attain the blend of the two worlds because she wills it; they simply come together to form this blend without her assistance. She remains passive throughout the play.
Thus, the character of Stella fulfills two basic functions. She is deeply involved in the battle between her sister and her husband. She is torn between the two factions unmercifully. But she is also the only one who can attempt to bridge the gap between these two arch enemies and all that they represent. She certainly does have some thoughts independent of the dynamic forces in her home; however, on the whole, she maintains a passive role.