This is 100% false. First physicians in nearly every country take an oath not to harm patients. Second, vegans often abstain from eating animals for ethical reasons and presumably the fictional vegan doctor here is motivated for that reason, and since humans are animals, she would not inflict harm on any animal, including her human patient.
(It’s true that a person could be vegan for religious reasons and refuse to do certain things under religious freedom, but again, letting someone die would contradict those religious beliefs.)
@Pat
Hitler was a vegetarian.