What do you think Stella knows occurred between Stanley and Blanche in Scene 11?

Stella knows what happened but refuses to acknowledge it..... she couldn't stay with her husband if she did.

STELLA:
I don't know if I did the right thing.
EUNICE:
What else could you do?
STELLA:
I couldn't believe her story and go on living with Stanley.
EUNICE:
Don't ever believe it. Life has got to go on. No matter what happens, you've got to keep on going.