Wonder Woman

Wonder Woman is a nickname for Nicolette Lau.

Chronologically, the first reference to Nikki as Wonder Woman is in episode 1x07, "Overkill", after the big fight scene:
 * Maria nodded, with a sidelong glance at Lau. She extended Lau's empty firearm, the slide locked open. Lau took it, exchanged the magazine, and re-holstered the weapon, as Maria said, "O.K. Corral. Bullets flying everywhere, and none of 'em hit you. You're Wyatt Earp."
 * "Actually," says Chaz, "that gunfight wasn't at the OK Corral. It was a block away--"
 * "On Fremont Street," Brady finished, with an eyeroll. He punched Chaz in the uninjured arm, and Chaz grinned. "Shut up, kid."
 * Lau held up her arms, crossed at wrists as if blocking something, hoping her hands weren't shaking visibly. "I am not. See these? Bullets and bracelets. Wonder Woman. Bulletproof."