sammily:
There are two main types of cheating husband, (Type 1) the one that just pick up a girl, maybe in a club, have his fantasies with her, forgets her and go back to his loving wife and kids. You may ask why he does that when he loves his wife, it could be that his wife does not give him what he likes, say mouth-action. The wife may not like doing it and the husband will not want to force her out of respect, so he goes outside to get his fantasies. He has absolutely no feeling for the outside hoes, just business.

The second (Type 2) are those that actually have a relationship with the outside hoes, like the OP's story. He spends time with her, pay for her accommodation, feeding and everything she needs. This is the worse type has the hoe is now competing with the wifey for the husband. In some cases, you wouldn't blame the husband for doing such, as wifey may have turned into a pain in the neck for the husband, no man wants to come home to a nagging, troublesome wife, so he runs to the peaceful arms of an outside hoe. The home suffers in this case.

Advise to the wifey, if you suspect your husband is in type 1 and want to screw back the missing nuts in his brain, when he's alseep, wake up and start praying for him, pray for his success, his promotions, his good health, pray for God to strengthen the marriage. He will hear you and if he's normal, he will surely regret his actions and come back to his senses. If wifey go about fighting husband, she might just push husband to type 2

Just my opinion.

It is hard to judge a wife being a nag.
Some men make women into what they are unfortunately.
The wife tells them as it is, but he doesn't like it.
The wife says it because she is loves her husband.

As usual children hardly out of pampers will soon start all kinds of text book postulations. Man was not created monogamous. The monogamous man is a creation of cultural assimilation. Monogamy is European culture. African monogamy is created when an African encounters and accepts the dictates of European culture as we see in Christianity and other types of cultural assimilation. I have one wife because I chose to be a Christian. It doesn't make me better than the man who has refused the deprivation of staying with one.