She lived her life to the fullest. She accomplished everything a person is supposed to accomplish in her life, so there is nothing to be sad about this, imo.
No; she did not live to be a grandmother to her younger children's children. She did not live to take care of Dog when he is old. She did not live to write her memoirs as an unique female bondswoman, or have another television spin off giving good advice to young wayward people. 51 is too young to die, especially for a beloved wife and mother.