Ordinary, a wife is expected to obey her husband. However, she is forbidden to obey if her husband requests something forbidden (e.g. anal sex).
However, there are matters which are doubtful, which we don't have a clear-cut halal/haram ruling about. Muslims are encouraged to leave doubtful matters, as per the Hadith:
The lawful is clear and the unlawful is clear, and between that are matters that are doubtful (not clear); many of the people do not know whether it is lawful or unlawful. So whoever leaves it to protect his religion and his honor, then he will be safe -- Jami' at-Tirmidhi 1205 [grade: sahih]
I'm wondering what a wife should do in circumstances where her husband requests something doubtful.
Question: Does a wife have to obey her husband in matters that are doubtful?
Possible examples of doubtful matters:
the husband requests a specific sexual act to be performed, but it's unclear if it's halal (perhaps something involving sex toys or almost-but-not-quite pornography);
the husband requests his wife to go out wearing clothes, where it's unclear if they adequately meet the requirements of hijab;
the husband insists she eats a certain dish (perhaps cooked by one of his relatives), but she's uncertain if the food is halal;
the husband distracts his wife from prayer until the exact last moment, when she has to perform it in a hurried fashion;
the husband requests his wife gets cosmetic surgery.
I give these examples to illustrate the question, but I'm seeking a general answer, not limited to these specific cases.