Andjele Vranjes claimed not to have seen Jannatul Bakya until it was too late, Wolverhampton Crown Court was told.
The 28-year-old estimated she was travelling at between 35 and 40mph – within the speed limit – on her way home from work when tragedy struck at 10.50pm on July 28, 2018, said Mr Robert Price, prosecuting.
Jannatul was a short distance ahead of her father Rafiqul Islam, who was holding the hand of her sister Sadia as they crossed dual carriageway Oldbury Road, Smethwick, on their way to the mosque in nearby Windmill Lane.
He saw a red Ford Fiesta with the defendant at the wheel leave a roundabout and continue towards the crossing without slowing down, it was said.
He pulled Sadia back and shouted at Jannatul to run but she was hit and flung 22 metres by the impact. She suffered catastrophic injuries and was certified dead at the scene, the court heard.
Vranjes came to a standstill after making an emergency stop but then drove off because she was worried and did not know what to do, continued Mr Price.
She stopped minutes later, called her partner and they both returned to the scene where she reported to police and allegedly asked one officer after being cautioned: "Can you tell if the light was green or red? I thought it was green but if it was red I take full responsibility."
The "green man" was illuminated for pedestrians and the traffic light had turned to red when the victim and her two family members started to cross, said the prosecutor. There was no CCTV of the incident.
It was claimed that the defendant conceded to police she could and should have regulated her speed and taken more care.
She said she suddenly saw a silhouette in front of her, realised it was a child and slammed on the brakes but it was too late.
Mr Price concluded: "She failed to see the red traffic light and drove into the girl. Her driving fell well below the standard expected and, as a result, the child died."
Vranjes, from Beakes Road, Bearwood, had no alcohol in her system, had a clean driving licence and is of previous good character.
She denies causing the death of the child by both dangerous driving and the lesser charge of careless driving. The case continues.