Medusa is a daughter of Ekidna's, and will be a reluctant member of her isolationist faction after the New Olympians make contact with the outside world.  She is the same age as Sphinx. 
Real World Background
Medusa is named after the most infamous of the three Gorgon sisters in Greek mythology. The Gorgons, named Medusa, Stheno, and Euryale, were three female monsters, the daughters of the minor sea-gods Phorcys and Ceto, with snakes for hair and feathered wings; their ugliness turned whoever looked at them to stone. Stheno and Euryale were both immortal and indestructible, but Medusa was mortal; some legends claim that she was originally a beautiful golden-haired maiden, but offended Athena by sleeping with Poseidon in one of Athena's temples and was consequently changed into a Gorgon as a punishment. Eventually, Medusa was beheaded by the hero Perseus, who afterwards gave her head to Athena; Athena placed Medusa's head upon her shield, bearing it there from then on. The winged horse Pegasus and the warrior Chrysaor sprang from Medusa's corpse.
Early in The New Olympians development (before it was co-opted into the Gargoyles Universe), Medusa was the original character in what is now recognized as Sphinx's role. It was soon clear though that Medusa's hair would be very difficult to animate if she was going to be a regular and nearly in every scene. By the time the show was pitched as a Gargoyles spin-off, Medusa and Sphinx had long been switched.