If the family member does not have a medical power of attorney or health care proxy, she can't remove your grandmother against your grandmother's will--though your grandmother can agree to go, even if it's a bad idea, if she (the grandmother) is mentally competent. If she's not mentally compentent and is following bad advice or otherwise doing things which are not in her own interest, you may need to bring a legal action to have a guardian appointed to make decisions for her.If the family member in question does have a POA in her favor or some other legal authority to act for your grandmother in a health care/medical capacity, you could only stop her by bringing a legal action alleging that she is violating her legal duty by not acting in your grandmother's best interest.From what you write, you should consult with an elder law attorney about your options and how best to protect your grandmother. It seems like it will likely take a lawsuit or other legal action in one form or another.