Police said she was Andrea Harris from Ardrossan.
The crash, involving a Stagecoach bus and an Isuzu 4x4, took place north of Ardrossan at 14:15 on Monday.
The 48-year-old driver of the Isuzu and the 36-year-old bus driver are "serious but stable" in Glasgow's Queen Elizabeth University Hospital.
Four bus passengers, two men and two women, are also in hospital.
They were taken to Crosshouse Hospital in Kilmarnock for treatment.
A further five passengers on the bus - three men and two women - received medical treatment at the scene or were taken to Crosshouse Hospital but were released after treatment.
The Scottish Ambulance Service declared the scene of the crash, near the Rowan Tree restaurant, a major incident. Two air ambulances attended, along with specialist trauma teams.
Police Scotland have appealed for witnesses to the crash.
Sgt Kevin Blackley from the Trunk Road Policing Unit, Irvine, said: "I would urge anyone who witnessed the crash, who has not yet spoken to police, or anyone with information that may assist our investigation to contact us through the non-emergency number 101."
A 45-year-old female bus passenger killed in a crash on the A78 in North Ayrshire which left six people in hospital has been named.