Lawyer Richard Josselson spoke after a juvenile detention hearing in Gloucester County. He called the girl a good student who plays soccer and softball, and he described her as "very distraught (and) very upset about what happened."
"This is a very good and just a very sweet girl," Josselson said. "She's an honor student and has never been in trouble before."
Six people were injured in the Saturday morning fire, including the girl. All have been released from the hospital or are recovering, authorities said.
Relatives at the courthouse said the teen had spent ninth grade with her father in Pennsauken, near Philadelphia, before returning last week to her mother and stepfather's home about 25 miles away in rural Clayton, where the fire erupted.
The teen is charged with two counts of aggravated arson and six counts of attempted murder. The victims were her mother and stepfather, who are both corrections officers, along with an uncle, his son and the girl's younger sister. The girl's 6-year-old brother was uninjured.
The Associated Press is not naming the girl because she is a juvenile.
Authorities believe the 2 a.m. fire started after gasoline was poured on the second floor, where the victims were sleeping. Smoke alarms awakened the family, and the adults helped rescue the children, one of whom suffered a hip injury when she jumped from a second story window. The fire was mostly contained to the inside of the new-model home. There's little damage outside.
The family moved in about three years ago, and the girl attended Clayton Middle School and briefly Clayton High School before withdrawing to attend school in Pennsauken, where her father lives and where she had gone to elementary school, according to family members and school officials.
She had returned to the Clayton home just days before the fire, relatives said. Her mother wanted her to stay in Clayton for 10th grade, but the girl wanted to live with her father, according to her 26-year-old cousin Edna Chavez, of Glassboro.
"She doesn't like being in that house," Chavez said.
About 20 relatives from both sides of the family sat outside the juvenile courtroom to support the teen, and some formed a prayer circle. Only close relatives were allowed inside the hearing, which was closed to the press.
The teen's father attended the hearing but declined to comment afterward.
Neighbors said the mother and stepfather were good parents who kept a close watch on their children. The family includes the mother's three children and the stepfather's son, an eighth-grader who wasn't home Saturday.
"They're very well-mannered kids," said neighbor Tina Siugzda, whose sons are friendly with the boys. "It's amazing the things that you don't know that's going on with kids sometimes."
The teen returns to court on Sept. 5 for another detention hearing. No dates have been set for a trial or preliminary hearing, according to Assistant Gloucester County Prosecutor Janis Melfi.