This is sort of a tangential spinoff to the heter for bc thread, where a wife uses bc without explicitely telling her husband, and it's a don't ask don't tell sort of thing.
Let's say Chaim Yaakov is sick on shabbos. Nechama Dina really thinks they need to buy medicine or take him to the hospital. Sender doesn't think so - either he's not sick enough, or he thinks they can wait till after shabbos, or this sickness isn't the type to warrant chillul shabbos, or whatever. However it happens, there's a disagreement and Sender thinks they should wait till after shabbos and Nechama Dina insists they must do something now, and she is prepared to drive Chaim Yaakov to the hospital.
Would you, as Sender, take the "sin" upon yourself to spare your spouse from getting what you believe to be a sin? Would you say, "Fine, then I'll drive Chaim Yaakov to the hospital or go to the pharmacy to buy the antibiotics"?
Would you sin in order to spare your spouse a sin?

<-- That's me, in this topic.