We should not seek to respect or protect "life" at the cost of human dignity, justice, and basic human rights.
Death is perfectly natural for all of us. We have medical technologies that can, at times, keep our bodies going for several years after all other functions have ceased (eg, respirators and feeding tubes). These technologies are unnatural and give us a false sense that we can extend our "life" without regards to our quality of life. It is a basic human right to chose medical treatment, and a basic right to refuse treatment when the treatment is futile, does more harm than good (like treatment of extremely severe burns, extreme treatments that will not cure), or even when the treatment is too expensive.
We also have the right to die with dignity. We can write in our wills and tell our loved ones a tremendous amount of our wishes, and legally our wishes must be kept as long as we provide legal and responsible means by which our wishes can be fulfilled.
Also in this case and in our culture (and Biblically for Christians), the husband has the first responsiblity to carry out the wife's wishes, both verbal and written. He is the next of kin. Be careful who you marry.