Sophie Taylor, 22, died when her car hit a block of flats in Adamsdown, Cardiff, in August 2016.
Cardiff Crown Court heard her BMW crashed while being followed by Melissa Pesticcio, 23, and her ex-boyfriend in separate cars.
Miss Pesticcio, of Llanrumney, denies causing death by dangerous driving.
She also denies causing serious injury by dangerous driving and two charges of dangerous driving.
Miss Taylor was allegedly being pursued by ex-boyfriend Michael Wheeler, 22, and Miss Presticcio, who was driving her own BMW, when she crashed into a wall.
Joshua Deguara, a passenger in Miss Taylor's car at the time, made a 999 call shortly before the crash which was played in court.
In the recording Mr Deguara, who spent a number of months in hospital after the crash, is heard saying: "We're being chased as we speak by a BMW One Series.
"Melissa Pesticcio is driving. Sophie is quite scared."
Mr Deguara claimed Miss Pesticcio had chased them from outside the home of Wheeler. He said she was "trying to cut us up" and "trying to make us stop".
Moments later Miss Taylor crashed into the wall after colliding at high speed with Wheeler's Vauxhall Corsa.
Wheeler has already admitted causing death by dangerous driving and causing serious injury.
The trial continues.
A woman allegedly killed by a love rival in a car chase called 999 for help shortly before her death, a jury has been told.