Like others said, just igmore it, what else can you do, she is nt willing to seek help, so if you talk about her personal life, she might get offended and in the end blame you if her marriage fails, which I hope it doesnt.
What I said about tell him a piece of my mind, is when he asks you about your marriage or other topics you dont want to discuss, then tell him firmly, that you would rathe not discuss your life matters with him and it is none of his business but of course, it should not sound rude but just firm.