I see. As you've observed Frank, you're not on the lease and if the rent doesn't get paid then the landlord won't be coming after you for it. You say she's moved out of the new rental and back to her town house, so it's very possible that she or the landlord has found another tenant to take over or replace the lease. Let's hope that's what has happened or will happen soon. If she's paying rent on a large house that she was expecting you to help with, she won't be happy and is thus more likely to be irrational and to stay in unwanted communication. So if she starts getting in your face about you paying for your share, remind her that you're not on the lease and that she's free to find a sublet.
The harassment of your wife isn't ideal either. You don't need for your wife to be constantly reminded of this mess. There's little that you can do about that, other than the obvious blocking of your ex's emails and telephone/cell numbers.
If you really want to take control of this situation, you could get a lawyer to write her a letter. That won't cost much at all, since it's just a letter. The lawyer would write that you're obligated to contribute to the rent, and that if she keeps contacting you and/or your wife that you are free to pursue criminal charges of harassment or seek a restraining order in civil court. Often that works effectively to put a stop to it.
However, in this case if your ex is continuing to have to pay that rent, she'll want to know how to put you on the hook for it. It's possible that she could bring an action against you in small claims court for half the rent, claiming that it was on the strength of your promise to move in and to help out that she signed the lease in the first place. I doubt she'd win but she could try, because if you made that promise or if she claims that you did then she has enough to start the case. I feel that I need to point that out to you. Again, even if she did try to get you on the hook for half the rent, she has an obligation to make best efforts to find a sublet in order to reduce what she's out of pocket; that's the plaintiff's obligation to "mitigate the damages".
Does that answer you? If there's more to discuss then please reply. If I've answered you fully then I'd appreciate a positive service rating please.