The mum of four young boys was just metres from her Midvale home when she was hit by a Nissan Pulsar around 6.15pm on Tuesday night.
Neighbours saw the horror unfold.
“I know who she is, so I was quite shocked to see who it was,” neighbour Peta told 7NEWS.
“It’s not something you want to see every day.
“I hope she pulls through because of those four little boys, you know?”
The force of the impact was so strong that it shattered the windscreen of the car.
Neighbours say they heard a car screech, followed by a loud bang.
They rushed out to find the 31-year-old mother on the other side of the road.
Police returned to the scene on Wednesday, questioning witnesses and marking skidmarks near the crash site on Wellaton Street.
Kay is in a critical but stable at Royal Perth Hospital and a man is assisting police with their investigation.
Her family is desperately trying to get clearance to fly to Perth to join her brother, who is already at her bedside.
They will have to apply from an exemption to enter the state on compassionate grounds.
The Premier’s office has confirmed their application for a border exemption has been prioritised and will be viewed favourably.
This article first appeared on 7News and has been republished here with permission.