The halachic position on this question is complicated for a variety of reasons.
There is a debate in the halachic world among experts as to the status of brain death in Jewish law. I personally subscribe to the position of my mentors that brain death does not constitute death; rather the cessation of cardio-pulmonary activity.
According to this viewpoint the existence of a fetus is a moot point; she would not be allowed to be disconnected from the ventilator by the virtue of her own life.
There is, however, an important caveat relevant to this case. In the worldview which says brainstem death is not the definition of death, this applies only to the brainstem death of a Jew. My mentors have ruled that this doesn’t necessarily apply to a gentile.
This is not because there’s any difference between the brainstem of a Jew or gentile. Rather, according to Torah law the gentile world is free to define the time of death for themselves as they see fit. (This is for reasons out of the scope of this discussion).
Therefore even in my halachic worldview, since Texas law defines brain stem death as a valid determination of death, the moral question of retaining her bodily functions for the sake of the life of a fetus is a valid question.
The Talmud rules that if the death penalty would be meted out to a pregnant woman, the court should not wait until she gives birth to carry out the penalty. This leaves room for debate; although we do not need to keep her alive for the sake of the fetus, would we be allowed to do so?
I am not issuing a ruling here, just raising points on both sides of the issue for the sake of discussion. At first glance it would seem that it is improper to keep the mother “alive” since this would probably cause pain and stress to the mother.
(Surprisingly, the medical world recognizes the experience of pain to a brain-dead patient. I was recently consulted by an anesthesiologist who was ordered to administer anesthesia while the brain-dead patient’s organs were harvested in order that he shouldn’t experience pain. This, to me, casts strong aspersions on the definition of brain death as death; when is the last time you heard of a dead man feeling pain?!).
Your final question is quite complicated to answer. The rule of thumb according to halacha is that no family member has a say in allowing even an act of compassion which would constitute an act of murder. Since, however, in the gentile world Mrs. Munoz was considered deceased by the standards of brain-stem death, halachically her family or her will would play an important part in the moral decision of how to deal with her situation.
This discussion, although it is dealing with a gentile patient, has profound ramifications for Jews who are bound by the Torah definition of death which is cessation of cardio-vascular activity.
For example, a Jew would not be allowed to sign a medical directive as an organ donor calling for the harvesting of organs after determination of brain-stem death but prior to the cessation of cardio-vascular activity. In most cases it also would disallow the detachment of a Jewish patient from a ventilator if the heart is still beating despite the determination of brain-death. These are serious questions which, when presented, as they often are in end-of-life situations, it is important to enlist the guidance of an halachic authority well-versed in this area.
Rabbi Yerachmiel Fried