Thank you, ladies for all your valued opinions.

I'm going to err on the side of letting it go and not talking about it. The reason of course is that I cannot conceive of her cousin (with whom her entire family is very close) not finding a way to let her family or her know the situation. Either way she will find out when the settlement happens. He doesn't have any money and since he owes tens of thousands, they would be right to ask questions before paying up. And maybe not. Cousin should take care of it. If I were family I'd be all over that.

If she finds out I knew something, I will tell her that I didn't feel right approaching it since I didn't have her husband's side of the story and it ultimately wasn't any of my business.

Financial ruin is not a possibility here. Financial set back is, but her family is pretty extensively wealthy and there's a finite amount of money that will be invested in the business. Also they have a prenup to protect her family's wealth.