That is what my hubby said, but I responded to her emails to let her know that I was aware of the activity and her persistence. He didn't want me to do such a thing and discouraged it, but I did it anyway for my own peace of mind.
She knew my husbands weakness, but she didn't know the woman behind the man. I really think it turned her off. She first started spamming me with all kinds of letters etc. he wrote, but it was all old news already. I was aware of the love affair and was willing to accept it for that and move on. If the shoe were on the other foot and I was the "other woman", I would hate being told by the wife to back off, I would feel insulted, I would move on, but that's me. I cannot speak for everyone.
I basically told her to get a grip on reality, what she claimed was hers is wearing my wedding ring, exchanged wedding vows with me, has given me his ring to wear and has never asked for it back. He lives in a home with me, we have a child together that he loves tremulously, and he is here day after day. Laughing with me, planning life and future with me, so he maybe a bit lost, that doesn't make him hers. I told her that if she really "loves him" she would put herself in his shoes and realize how confusing this all is for him, and how difficult she is making it. She wouldn't accept having someone pulling on her hubby's heart strings while he is committed to her. Of course she came back with, "he was the aggressor, he told me he is only with you because of the child you have together". Fine let him wait until the "child" has left home, and then you can have him. In the meantime he has made a commitment to be a family and it doesn't allow for extramarital affairs. I hope you will be able to figure it out. I think you have a right to stand up for yourself and it if feel threatened you have the right to eliminate the threat.
I guess you would need to be prepared to hear things from her that you may not want to hear.