Boundary - you will not live in an 'open' marriage where spouse seeks to have needs met out of the bounds of their vows, meets someone else's needs and deprives you of the same. You will not be friends with anyone willing to threaten the fabric of your marriage and destroy the foundation of your family...that includes spouse.
Tell her point blank, You are tired of all of the disrespectful behavior to you. you have had enough of the disrespectful behavior towards your marriage. You do not want your sons to live in a house where they learn that it is OK for a spouse to cross the boundaries of fidelity. You do not want your sons to learn that it is ok for their future wives to treat them or their marriages like she has treated YOU. They will learn the truth eventually.
To enforce this...see Sandi's WW spouse thread, there is a list of 5-6 immediate actions that should be taken by the betrayed husband including putting her out of the bedroom, you not providing any emotional support, companionship, financial support (not required by law at this point) and certainly no helping her with anything that would be what we would all call a duty of a husband.
Please re-read that thread extensively and JUST DO IT. DO NOT BE AFRAID OF HER BULL-$HIT. OK.
