The crash happened on Sunday morning on the A7 close to Aix-en-Provence. The woman, who had just left a nightclub, took the wrong entrance to the motorway and, after avoiding two other vehicles, hit a car travelling towards Marseille.
Three people travelling in the other car were killed in the collision. They were a couple and their brother-in-law, all aged between 30 and 34. Two other people in the car survived, including the 4-year old daughter of the couple who were killed.
"The little girl escaped virtually unhurt, apart from a few scratches, which is a miracle," investigator Dominique Moyal told AFP.