To what extent must a wife obey her husband?

A wife must obey her husband in what is right relating to marital rights, but not in sin or in what causes harm.
The Prophet ﷺ said there is no obedience in sin; obedience is only in what is right. So a wife may not follow instructions to abandon prayer, uncover her ʿawrah in public, cut family ties or do what is forbidden. Obedience also does not mean the wife may not hold opinions; the Prophet's ﷺ own wives discussed matters with him and gave him their views. The husband in turn must lead justly and consult. See Rights of husband & wife.