Fordola is a monster, but she is a product of... well, of Zenos' psychopathy. I don't think Lyse is being entirely fair when she blames Fordola entirely for what happened, but she's not entirely wrong either. Though her upbringing and situation can explain her actions, it doesn't excuse them; Fordola still chose to do what she did and should face justice for it.

That doesn't mean killing her, though. That means holding her to account for what she did.

I have little doubt Fordola will continue to play a role in the 4.x series ("So falls the hunter, but what of the hound?") and eagerly await seeing what fate has in store for her.