Guerri,
As I understand it, and I am not a lawyer, in the U.S. a mentally competent adult who is able to make decisions may refuse medical treatment for herself unless that refusal creates a risk to others. If the adult is not able to make decisions, the holder of her health care proxy may refuse treatment on her behalf. These rights override medical professionals' duty of care.
A child is not considered competent to refuse treatment, and an adult who refuses treatment on behalf of a child can be charged with child abuse - or potentially a more serious crime if the child passes away.
Specifics may vary from state to state. People who do not want their child to be treated in a particular way have moved from one state to another to find a legal climate that is more supportive of parental rights in this regard. Laws outside the U.S. may differ from the above in fundamental way. Where is this person located, is she an adult, and (if so) would a court (if it came to that) find her to be competent?
On a completely unrelated topic, I haven't seen your vote for KILDERKIN definitions yet. The deadline is still more than a day away, so you have plenty of time, but eight players have already voted. Did you get the list?
Efrem