I'm sorry you're in this mess. You don't deserve this crap from her.
IMO this is manipulative and a power play on her part.
You can't control what your wife says but you can control your reaction to it.
1 - "I'm sorry you feel that way but you have failed to prove to me that you're not in contact with the OM; and you have failed to prove to me that you are a safe life partner."
2 - Do not respond with anything else. Either say nothing (very powerful impact) and pretend you don't hear her; or respond with #1.
Any other reply gives her power over you and pulls you into her toxic/manipulative world. STOP playing her game.
FINALLY: Take your power back. Put her on the defensive.
Inform your wife that you saw the text etc and therefore know she's still in contact? The burden of proof is on her (not you).
Inform her mother that it is not over because she's still lying to everyone and texting him.
Does the mother live with her and help with the kids? Blow up your wife's toxic world. Consider taking a shot at the mother (since she wants to rugsweep) and remind her that she raised a liar and adulterer (and should be ashamed of her parenting).
You don't have to prove she's texting the OM. Under the circumstances (she's a liar and adulterer) she has to prove she's not.
[This message edited by Robert22205https at 12:55 PM, Friday, November 26th]