actually, you don't even NEED to show up. Just maintain the CREDIBLE THREAT of showing up.
If her and OM don't know what you're going to do, they then have to plan accordingly.
The problem with the answer you gave is that you are JUSTIFYING and EXPLAINING yourself to her. Your boundary ("I expect my wife to be faithful; I cannot abide a marriage where my wife is in inappropriate contact with another man") is self-evident, has already been stated (too often, IMHO) and needs no further explanation.
