Vanessa was created by George Perez, and she first appeared (as the Silver Swan) in Wonder Woman #171, August 2001.
Major Story Arcs
Vanessa 'Nessie' Kapatelis had the chance to meet Wonder Woman at a young age. When Wonder Woman first came to the United States, Nessie's mother, Julia, invited her into their home. At first, Nessie was jealous of Diana's beauty, but eventually the two got to know one another and formed a close bond, with Nessie loving Wonder Woman as an older sister. Only a high school student, Nessie dreamed of fighting evil alongside Wonder Woman.
Nessie had already been traumatized by her father's death when she was a child, but she was pushed over the edge when her best friend Lucy committed suicide. She began to blame herself for all the bad things that happened to the people she cared about. Doctor Psycho began causing her to have nightmares and, to help Nessie recover, the school counselor recommended that Wonder Woman leave the Kapatelis house.
Nessie recovered, but could not forgive her mother for making Wonder Woman leave. Eventually, she would start to blame Wonder Woman for abandoning her. Circe, in conjunction with Doctor Psycho, decided to use these mixed feelings as a way to use Nessie against Wonder Woman. Employing cybernetic implants and mental conditioning, they turned the young woman into a killing machine - the new Silver Swan.
After defeating Circe, Wonder Woman tried to help Nessie recuperate. However, Sebastian Ballestros, who had been behind Nessie's initial transformation, kidnapped Nessie and sold her to Veronica Cale, a woman who hated Wonder Woman. Cale ravaged Nessie's body even further, making her her even more of a cyborg and sending her to fight Wonder Woman once more.
Defeating Nessie again, Wonder Woman begged Dr. Leslie Anderson to remove Nessie's cybernetic implants once and for all. Nessie was then sent to Themyscira for recovery. It is presumed that after Themyscira vanished, Nessie returned to the care of her mother.
Vanessa has recently graduated from school. Wonder Woman as Diana Prince attended her graduation. They took some time for a quiet chat. It looks that all three Silver Swans no longer have the power or yearning to become the Silver Swan.
She has not appeared in the New 52.
Powers and Abilities
Having her powers derived from an experimental nanite treatment which she was supposed to regain her ability to walk again. The nanites however alter her physiology and drastically enhance her attributes beyond that of a normal human being. Vanessa would than be equipped with a metallic pair of cybernetic wings that would allow her to fly or use their razor sharp edges in combat, able to slice through concrete and mortar.
She was also able to project a devastating sonic scream with her enhanced vocal cords. This "swan song" was capable of various feats. Unleashed it could devastate a small area of land with destructive force. By creating a low-level humming, she was able to forma protective shield around herself capable of deflects bullets and other projectiles. She could either project them in short bursts or wide, longer attacks.
With additional cybernetic enhancement as Silver Swan her body was a cyborg but with the help of Wonder Woman and Amazonian doctors and Dr.Leslie Anderson, the cybernetic enhancements were fully removed.