A 15-year-old girl will serve time in prison for stabbing another teenager to death in Mount Vernon last year.

The teen - who News 12 couldn't show or reveal her name due to her age - spoke out for the first time. 

"I think of all the different choices I could've made that day that would've left Kayla alive and saved her family this heartache," she said. 

Families of the teenage victim and the one who survived didn't accept that apology.

"It doesn't take away from the fact that she murdered my daughter," said Lavern Gordon, Kayla Green's mother. "Her killer gets out in three years to live her life, have a family and have a career. My daughter will never see that."

Last April, 16-year-old Kayla Green and her best friend Mainece Simpson were stabbed near East Prospect and Gramatan Avenues in Mount Vernon hours after the city had celebrated its high school boys' basketball team winning a state championship.

"My daughter has nightmares, she can't be around knives, she doesn't like people in her space, and she cries herself to sleep at night," says Nicole Duncan, Mainece Simpson's mother. "All we can do is visit Kayla's gravesite and I'm trying to learn how to raise a grieving daughter."

Prosecutors say the feud stemmed from a longstanding rivalry between two local cheerleading groups.

"This was an intentional, senseless, and vicious crime." says Westchester Assistant District Attorney James Bavero.

The judge added that the defendant had a history of fighting in school, cursing out teachers and carrying weapons.

"It's a travesty that this young girl lost her life during an unnecessary and violent attack," said Hon. Susan Cacace, Westchester County Court judge. "These are not the only violent actions that the defendant has displayed throughout her short life."

The plea deal of three to nine years for manslaughter was less than the victim's family wanted after pushing prosecutors for months to charge the teen with murder.

"With our client's sentencing, the healing process can begin for the victim's family and for the community," said defense attorney Michael Borrelli. 

Both families say their hearts may never fully heal. The judge said the defendant was showing progress in detention and was hopeful she could still be a productive member of society after serving her time.

Westchester District Attorney Mimi Rocah released the following comment:

“A teenage defendant senselessly took the life of Kayla Green, and in doing so, left a community devastated. As a family and the Mount Vernon community remain in mourning, I want to reiterate my commitment to working with our vital community partners for meaningful violence prevention and intervention, especially for our youth. I know that nothing can cure the pain of losing a child. My Office will do what it can within the bounds of New York’s laws to seek accountability in these cases.”