Her first appearance was in the second series of the Teen Titans comics in issue #1.
She remained a regular member of that team until the events of Graduation Day when Nightwing disbanded the Titans.
Her powers are...well imagine a Green Lantern without needing the ring, and the creations aren't green, they're silver.
Argent made an appearance in Season 5 of the Teen Titans cartoon.
In the cartoon, Argent fired crimson energy beams which kinda blows the whole "Argent" thing but hey.