Been there and did nothing.....!! It’s the worst feeling and very humiliating..
1. Sue him for a divorce and make sure he pays the maximum with maintenance.. in other words the life you were accustomed to while you were with him and that you were to loose if on your own supporting yourself..
2. Sue her for enticement AND alienation from your husband
That ought to shut them both up...
Do it !!! you will feel better for it, otherwise you will always look over your shoulder as the one who was easy to get rid of while they enjoy the benefit of everything..
I agree men and woman like that MUST be taught a lesson.. it won’t last this relationship of theirs, but at least they will both think twice before doing it again..