Here goes Lo-retta:
She admits that her guy's a bit of a dog and not averse to chasing skirt, yet she loves him and wants to beat up his girlfriend instead.
Interesting, eh?
Wouldn't it be easier to kick his ass rather than everyone else's?
See, that thinking overlooks the actual goal that is motivating the action (and the decision as to which action to take). Before we can assess how well a particular action or reaction advances a particular goal, we have to accurately identify the goal.
In such cases, often the goal - not the facial one, but the one buried inside and usually denied on the surface, but which underlies our actions and forcefully compels our (seemingly) nonsensical decisions - is to restore our damaged ego by proving to ourselves that our betrayer, who has just hurt us and inflamed our fundamental insecurities by wanting someone else more than they wanted us, really does, in the end, still want us more than they want the other person.
So, with that goal (unconsciously) driving us, attacking the betrayer wouldn't do any good - it would seem likely to diminish whatever interest they might still have in us. On the other hand, our misguided (and probably now highly dysfunctional and desperate) reasoning mechanism might convince us that attacking the other person will make them less attractive, and us more attractive, to our betrayer. Perhaps it will make them look weak or demonstrate the depths of our conviction. Hopefully that will help our betrayer realize that it is us that they really want, and that they had made a mistake. Of course, that's not how it usually works, and if we had our wits about us we would understand and accept that. However, by this time our insecurities have overwhelmed us, our desperation is in charge, and our reason-based decision making has fled the scene because it didn't want to have to listen to the incessant emotional blathering that's taken the stage.
The result: it makes more sense to attack the other person rather then our betrayer. But, it would be hard to turn what I've just said into a hit song, so Loretta went with:
Now you've been making your brags around town that you've been loving my man ...
It wasn't a rough time to hold onto a husband. No different than other time period. That's been going on since Adam & Eve. 
