This is why it is really important for both spouses to understand that matters need to be resolved between them. You don't run to other people. It's not their relationship. They're not vested. And if the spouses go to others, it's typically going to be when things are bad. So of course the relative is going to advise that the relationship be terminated quicker than not. Again they're not vested, and it sounds bad.

Keep it in the house and work through it. The relationship will be stronger in the long run if it lasts, and if it fails, it'll be genuinely because of the internal relationship.