The attack that was captured on cell phone video and posted on social media.
The teen, 15, was taken into police custody Thursday afternoon. She along with three other girls, ages 13, 14, and 15, face charges that include aggravated battery and mob action, police said.
Details of the girls' identities have not been released because they are juveniles.
Judge Terrance Sharkey ordered the fourth girl to remain at home on electronic monitoring. She is charged with felony aggravated battery and misdemeanor batter in the July 22 attack.
The video shows the victim surrounded by at least five other teen girls and a teen boy before she's punched repeatedly as she screams for help.
Friends of the victim said the group offered to walk with the teen to the CTA Red Line, but said it was all just a set up so they could jump her and videotape the beating.
Cook County Assistant State's Attorney Nina Kelly raised concern for the girl's safety after threats to the defendants had been posted on social media, initially asking the judge to take the girl into custody for her own safety. The girl's mother and attorney said the concerns were overblown.
The girl will remain on electronic monitoring with an ankle bracelet, and is only allowed to leave home to go to school, church, or for a doctor's or dentist's appointment. She is not allowed contact with any friends or the other girls under investigation.
None of the other three girls charged have been taken into custody at this time.
The victim's family said the teen is currently in the care of the Illinois Department of Child and Family Services. The agency said it's investigating allegations of neglect.
Mervyn Jenkins, the victim's father, and community activists supporting him spoke to the media in part to address the allegations.
"I did file a report in a timely matter. I don't know how my daughter got there, but what I do know is... If it wasn't for one of the students, she wouldn't be found today by her school," Jenkins said.
"He physically searched for his daughter. We found him canvassing for his missing daughter, and I have no reason to believe he doesn't care," said Jedidiah Brown, a community activist.
DCFS said they've had prior contact with the victim's family and they are working with police to see what happened in this case.
At a Friday hearing, a judge ruled the victim would stay in temporary custody of DCFS until the family's next hearing Monday morning.
The victim's family hopes she will be relocated to live with a family member who is able to properly care for the teen.
DCFS released a statement Thursday night, saying, "DCFS is investigating allegations of neglect involving the 15-year-old with special needs that was brutally attacked this week. The tragic incident is heartbreaking. The department is committed to protecting the state's most vulnerable children. We are working closely with law enforcement to fully investigate what happened in this case. DCFS opened the investigation following a hotline call on July 23 and took protective custody of the 15-year-old on July 24. The department has had prior contact with the family."