Woah woah woah, I am not
being defensive of her actions. She sounds like a cold-hearted bitch, and it seems to me that if you give her the opportunity to do the right thing, she'll shit all over that opportunity. I'm just saying that we don't know her so we can't know that for sure. We can make an educated guess, but we can't know.
That's all. What I'm saying is that if OP gives her the opportunity to step up, and she does shit all over that opportunity, then she has no leg to stand on.
She'll have no way to defend herself. She'll have fucked up every single aspect of this.
Put another way, she won't be able to say to the husband, "I was going to tell you! I was just struggling with the guilt, I'd never hurt you," etc. etc. If you give her this opportunity, she has two options: take the high road, or crucify herself. There's no gray area to hide in. See what I'm saying?