You may consider saying this. " You may still be confused. But I am not. You are my wife. And I will not stand by while you ease yourself out of our marriage. You have said that you're not sure you can give our marriage 110%. I am letting you know now that if you see him again. I will consider that as you deciding that you can't make our marriage work. So the next time you go out, the morning after I will file for divorce. Further more, you will write a letter of no contact to him. I am not saying that you cannot see him. I am merely saying that if you do our marriage is over."

On a side note. Does your wife understand the damage she is doing to her relationship with her daughter. If she breaks up your family with the man who deserted her before. She risks her daughters hatred over this. I think your daughter needs to apply pressure on her as well, by saying that she not live with her or visit her if she destroys your family and hurts her father like this.