On the basis of your logic, if you're married with children and your spouse dies, you should be able to round up all the children and either kill them or let them fend for themselves because you shouldn't have to raise and pay for them yourself.
A Canadian conservative is one who believes in limited government and that the government should stay out of our wallets and out of our bedrooms.
They could let her die as she would have wished. Why does the end of her pregnancy suddenly mean there's a DNR? If there's no directive, at what point do you turn it off? Why is she worth nothing more than to be an incubator?She's dead. At this point you honor her wishes in life by removing her from the machines as soon as possible and by making sure her remains are disposed of how she would have liked, make sure that her property is bequeathed as she would have liked. That's about it. That's all you can do for her.
Who's going to take care of the fetus is a legitimate question. Seeing as how you're conservative I'm sure you're against the state doing so and so am I.