Defendant Alejandra Guerrero was 16 at the time of the incident on July 24, 2014, when 24-year-old engineering student Xinran Ji was attacked with a baseball bat and wrench while walking back to his apartment near campus after a study session.
She was convicted in October 2016 of one count each of first-degree murder, robbery, attempted robbery and assault with a deadly weapon.
On Friday morning, she was sentenced to life in prison.
Guerrero addressed the court at the hearing.
"I am so sorry and I pray that one day they could forgive me," she said.
Defense attorneys for Guerrero pleaded for mercy for the defendant, citing her abusive upbringing, but the prosecution reminded the court of her role in the violent attack.
"She watched as he was crying and screaming for help, and she didn't just watch, but she got down on the ground where he was and participated in the attack," said prosecutor John McKinney.
Jonathan Del Carmen, one of four people charged in the case, was accused of being the getaway driver in the attempted robbery. After pleading guilty to second-degree murder, he was sentenced Friday to 15 years to life in prison.
A third defendant, Albert Ochoa, is awaiting trial. Another assailant, Andrew Garcia, was convicted of first-degree murder and sentenced to life in prison.
Justice finally for murdered.@USCTrojans #FightOn grad student Xinran Ji from 2014? Prosecutor just told me 2 of 4 defendants will be sentenced today. Used bat in attempted robbery.@ABC7Courts pic.twitter.com/zWJEWQDdZs— Miriam Hernandez (@abc7miriam) July 13, 2018
Prosecutors said Ji was targeted in a group attack they described as "flocking." The suspects, prosecutors said, thought Ji would have money.
Ji's parents sent a statement to the sentencing Friday, saying in part, "We live in sorrow and darkness every day."