She had moved back in with her mother only days earlier, relatives said.
The mother and stepfather, both corrections officers, wanted her to start 10th grade in Clayton, they said.
"She doesn't like being in that house," a cousin, Edna Chavez, 26, of Glassboro, told the Associated Press. Chavez said she had assumed the tension was just "typical teenage" behavior.
In a show of support for the girl, about two dozen relatives from both sides of her family turned out for the juvenile detention hearing. She was described as a favorite niece and a good student.
The teen - referred to by authorities only as T. O. - appeared before Superior Court Judge Colleen Maier of the Family Court Division in Woodbury. The next hearing is scheduled for Sept. 5, the Gloucester County Prosecutor's Office said.
The teen is charged with six counts of attempted murder and two counts of aggravated arson, the Prosecutor's Office said.
Richard M. Josselson, the Haddonfield lawyer representing her, said he hoped she would be released after the next hearing.
Josselson said his client, who is being held at the Camden County Youth Center in Blackwood, is "very, very down and very depressed."
He described her as an honor-roll student who had never before been in trouble. She played soccer and softball during her freshman year and is a rising sophomore, he said.
"From everything I know about her, from everything her family has told me about her, what happened is completely out of character," Josselson said.
She attended high school in the Clayton area for the first part of the last school year, when she lived at the home of her mother and stepfather, Josselson said.
Josselson said she then spent close to the entire second half of the school year living with her father and attending Pennsauken High School. She had recently moved back with her mother in Clayton, Josselson said.
The girl's mother has been released from Crozer-Chester Medical Center in Upland.
Josselson said he had been hired by the girl's father to represent her.
Contact Darran Simon at 856-779-38209 or firstname.lastname@example.org, or follow on Twitter @darransimon.
This article includes information from the Associated Press.