Remaining firm in the force of her hurricane of craziness is great! You were even able to back babble her on things which left her confused. Shouldn't he be begging by now? Shouldn't he have moved out by now? Is my nail broken? Wait, he knows about the lawyer? heh, heh..
Keep being firm Choc, but remember kindness and compassion. She is so confused. Locked into a cycle that she can't get out of, at least in her mind. She's feeling physical attraction, probably something she hasn't felt for you in a long time and doesn't want to give that addiction up. She's afraid of losing that feeling and really, deeply afraid that it's her last chance in her MLC mind.
Her mind if full of attraction chemicals and she's an addict. As you keep saying, cold turkey in this matter of the OM is probably her only escape from this cycle. She has to have no contact with this man in any form, forever and she's the one that has to come to do the deed. It is all on her but be her guiding light. Show her love and compassion in your firmness. You're doing great!