A day, a week, a month, 6 months, Doesn't matter a bit. Doesn't matter. Hell honestly you should encourage her to understand the meaning of Koryo. Your boundary is lame. You do not understand.
She is infatulated with a man who is giving her something she has never experienced or hasn't experienced in a long time. It is a thrill. The thrill is a quest. And as long as he is unobtainable she will seek it, desire it, fantasize about it. Take it away and she will only want it more. Think about it. Here is someone pushing her to achieve her best, mentally, physically. Know herself, physically and mentally. Helping her to succeed in something she enjoys. Isn't this what we all want out of life: to feel great about ourselves.
You offer what? More of the same. More of the lame. What do you have that is unobtainable? That is something that she would want to fantasize about having day in and day out and do anything, lie, steal, cheat, to have? Nada. A boundary.
The most successful men in these situations dump their cheating wifes. A "you want them you can have them" attitude. Then go out a create something for themselves.
There is no success in being told: We are Separated. To respond with: I will give you a week to think if that is what you really want.
You encouraged her to have sex with other men in the past do you realize you are still exhibiting that same behavior.