She had been stabbed and cut several times, and her death has been ruled a homicide, KLAS-TV, Las Vegas, reported. Her body was found by a passerby Thursday and was identified by facial recognition, clothing and dental records, the TV station said.
"Of course our sympathies go to the family in this very, very difficult time," Coroner Mike Murphy said.
Jade was last seen by her family Dec. 21 with Brenda Stokes, a sometimes girlfriend of Jade's father.
"I'm here for justice and I'll be here every step of the way," Jade's mother, Te'Juana Reeves, told the TV station.
Stokes, who also uses the name Brenda Wilson, was being held at the county jail for allegedly cutting a coworker with razor blades at the Bellagio casino Dec. 21, the same day Jade's family last saw her alive with Stokes. She was being held on $600,000 bond.
Police said they found blood on Stokes' clothes and on the inside and outside of her car.
Investigators described Stokes as uncooperative, KLAS-TV said.