Do NOT ENGAGE the OW at all... don't even LOOK at her.
Do NOT argue. You show up, state your case. Explain that you LOVE your husband and your family and that you cannot tolerate OW attacking your home and threatening to break up your family this way.
Don't even LOOK at her.
If the OWH is not accepting of your claims just THANK him for his TIME, leave your contact info and LEAVE.
Do NOT turn this into a WAR ZONE. You MUST maintain COMPOSURE OR YOU will just be accused of being "crazy" or "controlling"
You must appear in the role of protective wife and mother ONLY.
Do NOT ENGAGE in argument with HER OR with HIM.
State your case AND LEAVE.
Notes :
1. It is very likley that the OW is NOT having sex with OWH right now.. Women having affairs usually engage in MONOGAMOUS invidelity.. that is, sexual activity is monogamous with ONLY the OM. 2. The OWH has likely noticed her distance and odd arrival times and goings on too. 3. He may not challenge her in PUBLIC.
All you need to do is showup with maturity and directness and leave. The seed has been planted by you in his head... that's all you need to do.
if he is more receptive, ie he knows alrady or suspected, etc. and wants to work with you to proove things, that's great... but do'nt PUSH it.
What you want is to visit her home and show her what it feels like to have a marriage attacked. Her H will do yOUR WORK for you on her end... HE will be WATCHING her more closely after your visit.. HE will be asking her questions and pressuing HER for more contribution to the marriage after yoru visit etc...
You need to learn to let the seeds grow on their own.. you just PLANT them and LEAVE.