Hmmm.
My take: Telling such story to her husband doesn't make sense.
Caroline shouldn't have told him the story at all. It'll create more confusion for Mike when she disappears, and makes him more angry to know Caroline couldn't even trust him with whatever challenge she has.
Besides the story is quite different from Caroline's situation. Caroline didn't kill Brenda willingly. She was kidnapped and reacted in self defence! Most people don't go to jail just for self defending themselves against harm. Who knows, maybe if she has trusted Mike at all, it would have been different. Her husband's family is well to do. Maybe they would have found her a good lawyer to fight her case.
But I guess the Author just want to her story her own way.
Li_Mian