Her twin brother, Victor, was in the front seat, critically burned by a chemical, authorities said, and their father was lying on the ground nearby, unresponsive. Police said the father doused the boy with a chemical so toxic it sickened rescue workers.
The father, Jorge Barahona, also apparently put gasoline on himself in what he later told police was a futile suicide attempt by setting himself on fire.
Jorge Barahona has pleaded not guilty to attempted first-degree murder in the injury of Victor, who has been released from the hospital.
Authorities haven't said how Nubia was killed.
Carmen Barahona also faces seven counts of aggravated child abuse and seven counts of child neglect. Her attorney didn't immediately respond to an e-mail, and police refused to elaborate on what led to the charges. The head of the police department was expected to talk to the media Monday, according to the agency's news release.
State child welfare officials have come under heavy criticism over missed opportunities to help the twins after an anonymous abuse allegation was called into a hotline Feb. 10 -- four days before the children were found.
The caller said the twins' feet and hands were bound with duct tape and they were kept in a bathtub as punishment. Child welfare officials also believe the girl was being starved.
The officials have described a disturbing picture of a Jorge and Carmen Barahona, who adopted the twins, an 11-year-old autistic boy and a 7-year-old girl from foster care. The couple has been the focus of at least three abuse allegations in the past several years, but nothing ever came of them.
