[Gorgo, Source: About.com]
According to Herodotus, her father valued her insight and judgment. The one glimpse we have of her life before her marriage shows him refusing to send her out of a diplomatic meeting. It turns out the diplomat was right to want her to leave. She saw through his attempt bribe her father into joining a doomed rebellion and prevented it.*
When her father died, she married his half-brother, King Leonidas I,** and continued to act as king’s advisor. There is some evidence that she traveled with him on at least one of his visits to Athens. One of the quotes Plutarch attributes to her shows that she knew something about Athenian theater, likely through having gone to see it. When an Attic woman made a comment about Spartan women lording it over men, Gorgo is said to have replied that only Spartan women were mothers of men.
When news arrived of the Persian king’s plan to invade Greece, it did not come in the regular way. A blank wax tablet was sent to Sparta, much to everyone’s confusion. It was Gorgo who figured out the trick of it and ordered someone to scrape away the wax. The message was written on the wood underneath to keep it from being intercepted.
We know nothing of her life after her husband died in the Battle of Thermopylae. Her underage son took the throne with his uncle (her brother-in-law) as his regent. To be honest, it would be surprising if she didn’t continue to act as king’s advisor.
*Herodotus says she was eight or nine at this point, but it’s entirely possible he made this assumption based on the fact that she was unmarried and ignored the fact that Spartan women married much later than women in other Greek city-states.
**Yes, that Leonidas.
Herodotus, Histories Book 5, 5th century BCE - Sacred Texts Archive
Herodotus, Histories Book 7, 5th Century BCE - Internet History Sourcebooks Project
Plutarch, "Gorgo," Sayings of Spartan Women, 1st century CE - Lacus Curtius
Gorgo, Queen of Sparta - Wikipedia
Cleomenes I - Wikipedia
Leonidas I - Wikipeda