I remember that it's a series by Ursula Le Guin, who I adore, but I can't remember the title and find the books.
It's a collection of connected histories of three planets in different systems. There is a war, someone tries to turn off, someone tries to turn on.
A young officer has to go. He goes into his spaceship with his whole family for a voyage in hibernation lasting maybe 1000 years. His mother doesn't want to go. She says behind alone, though with a plant. In time she discovers strange beings and learns to communicate with them. They don't want to speak to anyone else, so she becomes their ambassador. She dies, happy and honored, while her son still hasn't reached his destination.
Please help me remember.