My aunt's friend died at 58 and she was vegan?

She died suddenly with no warning, symptoms, no previous illness, just died and the doctors don't know how. She was a raw vegan. My family knows that I am a vegetarian trying to become vegan and they think I will end up with the same fate. They feel extremely convinced that her death was diet related, because they always say "Oh, vegetarians and vegans don't get much protein; they're going to whither away and die". She's been a vegan for many years before. I think their claim is uneducated and misguided. I feel convinced that having a vegan diet if done properly is extremely healthy, but they [my family] think I'm crazy about my beleifs. What should I tell my family? How can I convince them that vegans and vegetarians don't whither away and die, instead thrive?