The 16-year-old girl was critically injured in the crash in Kingswinford three months ago but her condition has now improved and she is continuing her recovery at home.
Driver Joshua Parkes and passengers Lucy Tibbetts and Isabelle Floyd were pronounced dead at the scene when the Skoda Fabia they were in crashed into a tree in Bromley Lane on the evening of October 13.
And front-seat passenger Nathan Cartwright died from his injuries at Queen Elizabeth Hospital in Birmingham four days later.
Joshua was aged 21, Nathan was 18 and Lucy and Isabelle were both 16.
A spokesman for West Midlands Police said: "The fifth person involved in the Kingswinford Bromley Lane crash, the injured girl, is now out of hospital and is continuing her recovery at home."
Dozens of tributes were left at the scene in the aftermath of the crash including flowers, balloons, clothing and cards.
The families of the victims were left upset when some of these were removed just before Christmas, but the tributes have since been handed in to the police anonymously.
The Independent Office for Police Conduct has launched an investigation into the level of involvement of West Midlands Police due to the fact the Skoda came to the attention of officers before the crash happened.
West Midlands Police, which is conducting its own investigation, said the police car wasn't in the "immediate vicinity" of the Skoda at the point of collision.