Pictured: Pedestrian killed by 'drunk driver' allegedly four times over limit

The man accused of mowing down a young female pedestrian in Sydney's south was allegedly four times the legal blood alcohol limit at the time of the crash.

Irish national Patrick Nealon allegedly ran a red light on the Princes Highway at Wolli Creek just before 6pm on Wednesday, and hit Sydney student Nicole Lewanski.

Ms Lewanski's family said the 22-year-old had been walking home from her "dream" librarian internship with the University of Technology in Sydney, which she had begun just six weeks ago.

"This person is going to have to live with that forever now," Ms Lewanski's brother Steven said.

"She was a passionate feminist, she was always sticking up for her friends and others."

Witnesses said Ms Lewanski was standing on a pedestrian island in the middle of the road when she was struck with a "loud thud" and thrown along the highway by Nealon's out-of-control ute.

Nealon will now spend Christmas behind bars after he was refused bail in court on Thursday on a string of charges, including aggravated dangerous driving causing death.

Moments after the crash Ms Lewanski was treated by onlookers who raced to help, and later paramedics, but she died shortly after from massive head and internal injuries.

"Police from St George Local Area Command were called to the scene locating a 22-year-old woman who was unconscious in the middle of the road," NSW Police said in a statement.

"She was treated by NSW Ambulance Paramedics at the scene before being conveyed to St George Hospital where she later died."

It's alleged Nealon was found near the crash site and arrested by police after allegedly refusing a roadside breath test.

A mandatory blood and alcohol test later returned a positive reading of 0.199, police said.

Ms Lewanski's father Henry Lewans described his daughter as a "beautiful girl" and said she was "in the prime of her life".

Nealon is due to appear in court again on January 10.