Somehow you have to beat her at her game. You need to be the one building up husband's ego and you need to become the fun one and lose some of that responsibilty (get sitters and go out), be seductive or whatever the heck she is, and when you get a call from OW about your husband "still cheating" remind OW that he's cheating on her!!!!! AND, he's still married to you.... that makes her desperate AND stupid!
There is no arriving, ever. It is all a continual becoming.