After her father died of an aneurysm on the way back from a family camping trip, Sue's mother married scientist Roger Nero. Nero was searching for the genetic key to release innate megapowers in humans, and began experimenting on the teenaged Sue, her brother Carl, and Nero's daughter Darcy in his basement laboratory. After a few years of tests, Nero unlocked Sue's powers of atomic fire, which unfortunately set the lab and house ablaze. Sue's mother perished in the fire, and the bodies of Nero, Carl and Darcy were never found. Sue was taken in by family friend and millionairess Darlene Stenbaum.

After college, Sue married Nick Buso, a man she had met there. Buso eventually became physically abusive, and Sue finally used her fire powers to threaten him and drive him off. After their divorce, Stenbaum gave Sue a job as Stenbaum's personal assistant. During a battle at one of Stenbaum's construction sites between Captain Defender, Pixie, Blackrock, Lavender Valentine, and Shatter, Sue used her powers to help drive off the villains. She was invited to join the Keepers, and decided to do so as Whitefire.

Whitefire can generate atomic flames from her body which can dissolve the bonds between atoms, causing greater damage than normal flames of the same temperature. She can also fly.