Born in 2210, Grayson was a schoolteacher from Earth who married the Vulcan diplomat Sarek and gave birth to Spock in 2230. She reunited with her son when she accompanied her husband aboard the Enterprise during the Babel Conference in 2267, and was instrumental in helping Sarek and Spock reconcile some of their differences. An emotional woman, Spock wondered why his father would marry her, to which Sarek replied it seemed like the "logical" thing to do at the time.

In an alternate reality accidentally created by a temporal survey team using the Guardian of Forever on stardate 5373.4 (2269), Amanda separated from Sarek and returned to Earth's solar system shortly after young Spock's accidental death on Vulcan in 2237 (8877 on the Vulcan calendar); she subsequently died in a shuttle crash near Lunaport. When the adult Spock from an alternate future altered time to prevent his own death as a child, the timeline that led to Amanda's death was erased as well.

In 2285 Amanda helped Spock re-educate himself after his death and rebirth on the Genesis planet and fal-tor-pan rejoining. She tried especially to help her son rediscover his human side, by programming his computer to ask such questions as "How do you feel?"

Amanda was Sarek's second wife. After her death he married another human woman named Perrin.