That is a really hard situation and I feel for you. It is impossible to know what is right to do, or what is best for those involved given the complications, plus the sense of dignity people deserve. It is obviously easier to go into nursing care, but what happens to quality of life for both mother and father? Is it better to have them together and experience those last times together? Is your father able to care for her enough, or will it be a burden that is too much for him, especially emotionally?
Whatever you choose, I am sure you and your family will make the right decision for all considered. Sometimes I think that unless we can prolong mental acuity, we shouldn't be putting too much effort into prolonging life. I don't mean that in a cruel way, but from my own perspective. The worst thing that could have happened with the stroke is that people would be forced to look after me. Death is preferable to that for me.