The collision, which involved a silver Renault Clio, silver Mercedes C220 and a blue Audi A6, happened at 6.50pm on Tuesday, May 31.
Police said the woman driving the Renault was taken to hospital with serious injuries and subsequently died on Thursday, June 16. She hadn’t been named at the time of going to press.
A Leicestershire Police spokesman said: “The Renault was travelling along the A607 towards Croxton Kerrial and the two other vehicles were travelling in the opposite direction when the collision occurred. The driver of the Mercedes wasn’t injured and the driver of the Audi sustained a minor facial injury.
“We would like to speak to anyone who saw the collision or any of the vehicles beforehand. Anyone with any information is asked to contact Dc 1837 George Dodson on 101, quoting incident 580 of May 31.”