Officials did not provide any further information on the girl's condition or if any of her family members had been trapped.
Emergency workers used search dogs and helicopters to rescue dozens of people stranded in mud-coated rubble in the normally pristine area, sandwiched between the ocean and the sprawling Los Padres National Forest, about 180km north of Los Angeles.
The searchers are using all-terrain vehicles and helicopters, but downed power lines and blocked roads are complicating their efforts. Authorities said at least 13 people have died and 28 were injured as a result of the rain and flooding.
Winfrey, 63, took to Instagram to share photos and videos of her home in Montecito, Calif., which has been damaged by the natural disaster.
An area above Montecito called Romero Canyon has been cut off completely from the outside world, and rescue teams are trying to evacuate several hundred residents trapped there.
The upscale communities of Montecito and Carpinteria, just outside the city of Santa Barbara, were hardest hit. Before, he posted that he was under mandatory evacuation.
But the wooded hillsides that once gave their estates a sense of seclusion were largely denuded by last year's historic wildfires, setting the stage for the massive slides that slammed into homes, turned highways into raging rivers and shredded cars into almost unrecognizable tangles of metal after heavy Tuesday rains.
After a wildfire, burned vegetation and charred soil create a water repellent layer which blocks water absorption.