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 in a crashed car beside her partner for three days, despite the accident being reported days earlier to police, has died.
Lamara Bell, 25, was left critically injured and her boyfriend, John Yuill, 28, died following the crash at the M9 near Stirling last Sunday. The incident was reported to police that day, but officers did not attaend the scene for 72 hours after another call.
Ms Bell was taken to Glasgow's Queen Elizabeth University Hospital but has now lost her fight for life, her brother confirmed on Facebook.
Martin Bell stated: "My sister just passed away."
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.