Stella is the mediating point between Blanche and Stanley. In many ways, we can interpret the conflict between Stanley and Blanche as a territorial battle over who gets Stella’s love and affection. Nowhere is this more clear than in Scene Four, when Blanche rails against Stanley in what is essentially a scene-long tirade while he stands outside (for the latter half, anyway) and listens in. When he finally enters, “Stella […] embrace[s] him with both arms, fiercely, and full in the view of Blanche. He laughs and clasps her head to him. Over her head he grins through the curtains at Blanche” (4.126). And round one of the battle goes to Stanley.
But the fight is far from over. Stella comes to her sister’s defense against her husband time and time again, starting with his accusation of a “swindle” in Scene Two and continuing as he uncovers more and more information about Blanche's past in Laurel. Stella remains firmly on her sister’s side, refusing to believe these stories even in the face of overwhelming evidence. “You didn’t know Blanche as a girl,” she argues. “Nobody, nobody, was tender and trusting as she was” (8.50).
This is what we most have to remember about Stella – that she knew Blanche when they were both girls. It goes a long way in helping us understand her loyalty and kindness to her sister. However, it makes it considerably more difficult for us to understand her decision at the end of the play to disbelieve her sister, send her off to a mental institution, and side with Stanley. So what does Stella possibly use to justify her decision?
“I couldn’t believe her story and go on living with Stanley.” (11.24)
Interesting! Stella says she can’t believe the story if she wants to go on living with Stanley. She doesn’t say that she thinks Blanche is lying; rather she’s consciously choosing to think Blanche is lying so her life can continue without interruption. Does this sound like self-delusion? A retreat into a world of fantasy in order to avoid dealing with reality? Does this sound like (gasp!) the very same thing Blanche is doing?
On the one hand, this is pretty awful on Stella’s part. She has good reason to suspect that her husband raped Blanche and drove her over the edge to insanity, but she’s pretending it never happened. On the other hand, Stella really doesn’t have another option. (Even more interesting is the fact that Blanche used this same argument to defend her own self-delusion.) Or, as Stella's neighbor Eunice says, “Don’t ever believe it. Life has got to go on. No matter what happens, you’ve got to keep on going” (11.25).
This line in particular is fascinating because it so much sounds like survival instinct. These words, “survival” and “instinct,” should ring a bell with you. They should send you back to Blanche’s tirade against Stanley in Scene Four, when she tells her sister that Stanley represents ape-like primitivity, the law of the jungle, and that Stella should move forward and progress with the world out of sub-human darkness. She begs her sister, “Don’t hang back with the brutes!” (4.118). In fact, by obeying a primitive survival instinct instead of considering morality or loyalty or even logic, Stella has done just that. She hangs back with the brutes not just by staying with Stanley, but by catering to the animal impulse of survival over all else.