Many readers often confuse 'Ms. Liberty' with 'Miss Liberty'. Miss Liberty is the daughter of Statesman and Maiden Justice (Lord Recluse's sister). Ms. Liberty is Miss Liberty's daughter, granddaughter of Statesman. She is also his sidekick.
Megan has several Statesman-like powers she inherited from birth, but she also carries around a few extras. An inheritance from her grandmother is the Liberty Belt, also known as the Girdle of Hera, which was a wedding present from the Furies. This belt gives the wearer 'powers of the goddess'. Another artifact she carries is the one true Excalibur, which she cannot use. This sword was carried by Hero 1, until he gave it to Miss Liberty before his one-way trip to the Rikti Homeworld. Ms. Liberty now carries it for the day when he returns.
Ms. Liberty has recently taken on several heavy responsibilities. In addition to leading the Vindicators, the team of Freedom Phalanx sidekicks and former sidekicks, she founded the Longbow branch of Freedom Corp (which was itself founded by her mother). This makes her perhaps the primary hero in opposition to Lord Recluse's Arachnos, even more so than Statesman himself. It is likely he will see fit to unleash his supervillains on her before long.
Ms. Liberty is the trainer for Atlas Park, and as such is perhaps the first major NPC many new players see (while Galaxy City is an equal choice for a starter zone, Atlas tends to be much more popular).