Riley Boyle, 17, was in the shower when the fire broke out close to the rear entrance of the 2½-story Bonnie Way home around 5:30 p.m. Saturday, responders said.
The flames quickly spread to a rear hot tub room and a pergola-covered porch, trapping the victim in a bathroom just above the blaze, they said.
The Northern Highlands Regional High School junior was removed from the bathroom and later pronounced dead at The Valley Hospital in Ridgewood after CPR efforts at the scene.
Her older sister, Cassidy, who was also home with a family friend when the fire broke out, got out OK, neighbors said.
However, a pet dog and two cats who apparently were in the rear room also perished in the fire, they said.
The teens' parents weren't home at the time, they said.
Riley was a stellar student-athlete who maintained a 4.0 Grade Point Average, as many who spoke of her pointed out.
She was, as one put it, "an incredible role model for her peers."
Her family released a statement through attorney Ronald Dario:
"Our hearts are broken as we struggle to make sense of this terrible tragedy. Our only solace is in the outpouring of love from the community that shows us how in her mere 17 years, Riley has touched so many hearts.
"While we are grieving in private and appreciate your respect for our family, our community coming together gives us a glimmer of light in our darkest times.
"Thank you all."
Northern Highlands Regional School District Supt. Scot Beckerman said the popular junior's death "leaves a significant void in our community and our hearts."
NHRHS Principal Joseph Occhino said he, like many others, was feeling "great sadness and a very heavy heart.
"We are deeply saddened by this news," Occhino wrote. "The entire school community extends our heartfelt thoughts and prayers to the Boyle family during this very difficult time."
Northern Highlands had a delayed opening Monday so students, teachers and staff could receive counseling from its Crisis Response Team, Wellness and Guidance departments and Child Study Team.
They were, assisted by counselors from North Jersey Health and Wellness and other area high schools.
"This definitely affected many people: family, friends, students, neighbors, emergency responders," Allendale Police Chief Michael Dillon said. "It's raw for everyone."
Firefighters and EMS workers were visibly shaken at the scene on Bonnie Way on Sunday. They'd come from a dozen or so area towns as far away as Suffern, NY, to assist their Allendale colleagues.
"Some are very bothered by what they saw. We're all so sad," one firefighter said once the blaze was extinguished. "That poor kid...."
Allendale firefighters were joined by their colleagues from Franklin Lakes, Ho-Ho-Kus, Ramsey, Mahwah, Oakland, Saddle River, Upper Saddle River, Waldwick, Wyckoff and Suffern.
They had the bulk of the fire knocked down in about a half-hour. They needed considerably more time, however, to fully extinguish what became a four-alarm blaze that severely damaged the million-dollar home.
EMS units from Allendale, Ramsey and The Valley Hospital in Ridgewood also responded, along with crews from Orange and Rockland Utilities and PSE&G.
A regional Critical Incident Stress Debriefing unit also was requested to counsel responders.
An official cause of the fire will be determined once an investigation is complete -- although responders said it appeared accidental.
Meanwhile, a classmate of Riley's has launched a petition to name the running track at their school after her.
SEE: Classmate Petitions To Have HS Track Named For Bergen County Teen Who Died In Tragic Fire
Click here to follow Daily Voice Mahwah-Ramsey and receive free news updates.