If you want any respect from her (or any respect for yourself) then you will let her know that she has to cut all ties to the OM immediately and forever. You can't allow yourself to be treated this way. To be kept in a marriage where one person doesn't consider the other as a partner. If she doesn't stop seeing the OM then get the D going.
I don't know your history, but you sound way too nice to her. You need to set some boundaries on what's acceptable and hold her accountable.
