Lamara Bell, 25, who lay in a crashed car off the M9 near Stirling for three days, has died, her brother Martin Bell said.
Her partner John Yuill, 28, died in the accident. Police have apologised to their families for the delay in providing help.
Scotland's Justice Secretary Michael Matheson has now launched an urgent review into how the police handle emergency calls.
A woman who lay injured in a car crash for three days before it was reported to police will be in hospital for months, her mother said.
Lamara Bell, 25, was seriously injured and her boyfriend John Yuill, 28, died when their car went off the road on the M9 near Stirling, Scotland on Sunday.
Miss Bell, who has two young children, is currently in a medically induced coma at Glasgow's Queen Elizabeth University Hospital.
Her mother Diane Bell told the Scottish Sun: "She will be in hospital for a good few months. We don't know what she is going to be like [when she comes round]."
Scottish police failed to react to a call over a fatal car crash because the information was not logged on their systems.
An investigation has been launched over fears a couple involved in a fatal road crash may have lain in their car for days.