Meh, let her die.
She knows, or at least 'knows' what she wants. She knows the risks of not taking the blood transfusion. I think we put too much emphasis on both the choices others make, and on the value of human life.
Don't get me wrong, living can be pretty sweet, but you don't sign a contract with 'god' guaranteeing your 76.4 years. Some people die before others, that's just life.
Or lack thereof, i suppose.