What causes Desiree to take her child and disappear into the “deep, sluggish bayou”? Does the reader sense any regret from Armand as a result of this double death at this point (or ever, in the story)? Why/not?

We can see Desiree's attitude at the point when she leaves Armand is more resolute, focused, and uncompromising than at any other point in the story. She leaves with her baby and ostensibly dies in the wilderness. Ironically, it is at this point when she shows strength - the strength to leave and not look back, to not make agonizing pleas to Armand to keep her - that she makes her more fatal mistake. She could have returned to her parents, who would have accepted her and her child. She acts and asserts herself in a way that would have greatly helped had she done so earlier in the story, had she stood up to Armand, demanded proof rather than believe mere speculation, and gotten her parents involved. I don't think Armand shows remorse at all.

She disappeared among the reeds and willows that grew thick along the banks of the deep, sluggish bayou; and she did not come back again. p. 181