Good thoughts. Personally I think there is a big difference between a spouse that is still at home and cheating, in which case it is still a shared home, and a spouse that has moved out and is coming into one's own home to practice infidelity. My undertstanding is that her spouse is not living at home.
It hurts the R and oneself not to enforce boundaries. She set a reasonable boundary that H not engage in activities related to infidelity in her home. He violated that boundary.
Protecting oneself financially when one's spouse is out of control is not reacting out of anger, it is taking the situation at face value (no one knows what will happen) and acting responsibly.
Her H is going to visit another country to visit OW. This is a very significant expense, emotionally and financially. There is nothing wrong with her H feeling as though he is putting his marriage at risk by doing this. He needs to understand the stakes. More important, she needs to have a safe space during this process and my suggestion that she secure her household is related to that, not a way of punishing her H. This should be about her, not him. She needs to accept that he may not return and do what it takes so that she can be happy and secure not matter what happens. Giving someone access to one's own home--it is not his home now--to practice infidelity does nothing to help in terms of that goal.
And, like my C used to say to me, let him see your anger and pain once in awhile. Acting like all is hunky dory just lets him stay in his comfort zone.
It is time for her to let him go for awhile and see what happens while she works on herself and takes care of herself.