The teen was left fighting for her life when the car she was a passenger in collided with a tram at around 6.30am on Thursday morning.
By Friday morning her condition was said to have stabilised but she remained critical on Monday morning, West Midlands Police said.
Meanwhile a teenager suspected of driving the car while over the alcohol limit has now been released on bail as police investigations continue.
He had also been taken to hospital but was not seriously hurt, while a passenger on the tram suffered minor injuries.
The crash happened at the Bilston Street Island in the city centre and part of the roundabout was shut for much of the day in the aftermath of the crash, which left a West Midlands Metro tram and the Vauxhall car the teenagers were in badly damaged.
It was the fourth time in four years that a serious crash involving a tram and a car has happened at the roundabout, which is next to the old Royal Hospital and Wolverhampton Crown Court.
The tram line runs through the centre of the island which connects the ring road, the A41 Bilston Road, Bilston Street into the city centre and the A454.