You would do best just not to talk to your H at all. He WANTS to charm you all over again ... He's getting OFF on having two women pining away for him. And he uses lies to drive that to happen.
She wants your H to file for D, but he's too cowardly to do that.. its too much work. He is likely going to wait for YOU to do it... so just don't. OW will get fed up with him and turf his arse...
This does NOT mean YOU take him back... it means he has no one and hopefully learns something about how useful deceit is in managing relationships.
Until he demonstrates visibly to you that he's a different man, No Contact.