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."

US national Joshua Samuel Aaron, 32, was held at New York's JFK airport and will appear in court on Thursday.
He is one of three men accused of illegally accessing the personal information of 100 million people in 2012-15.
Twelve major institutions were victims of the hacking, including JPMorgan.
Mr Aaron had been a fugitive living in Moscow, but flew to the US voluntarily to face the charges, his lawyer said.
In a statement on Wednesday, US Attorney Preet Bharara said: "Joshua Samuel Aaron allegedly worked to hack into the networks of dozens of American companies, ultimately leading to the largest theft of personal information from US financial institutions ever."
The other two suspects are Israeli men: Gery Shalon and Ziv Orenstein. They were arrested in Israel in July 2015, and extradited to the US in June 2016.
All three men were charged in November 2015.
They allegedly manipulated stock prices by selling shares of companies to individuals whose contact information they had stolen.
The men were also charged with running an illegal payment processing business that they used to collect $18m (Â£14.3m) in fees.
Prosecutors claim the men hacked into competitors' systems to spy on them and then hacked into a credit card company investigating their payment processing business in order to avoid detection.
The company hit hardest by the breach was JPMorgan. More than 83 million of the bank's customers had data stolen in the breach.

Based in Doncaster, he simply asked a bunch of strangers: "What do you want?"
With support from the Arts Council England, the results have been put on display in the Frenchgate Centre, Doncaster.
"The project became led by the answers that subjects gave," says Monaghan.
"Political and societal changes have rendered us all as individual consumers, those portrayed have been photographed alone, but when exhibited they are grouped together and their desires for health, happiness and a better world coalesce.
"We want the same things, we want to get along, we want to be social, we want community."
Monaghan also points out that, of the 150 on show, only one wanted a commodity.
Here is a selection of pictures from the project.
You can see more work by Les Monaghan on his blog.
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.
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FBI and US secret service agents have arrested a man charged with the largest cyber-attack of financial firms in America's history.
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There are times when it is best to keep things simple, and that's just what Les Monaghan has done for The Desire Project.