Two of my friends did. One got a very sympathetic response - the OW did not know she was the OW! They met up and confronted him together and both dumped him. In the other case her DP got the OW to contact her to deny anything was going on and to claim her dp was meeting her to support her as she was coming out as gay. All lies. And once this was established my friend then messaged her asking her where her self respect was and saying her lies had made his betrayal so much worse. There was no reply but the OW finished with him - and so did my friend.