The car, coming from Ahmedabad to Makrana town, hit the divider near a village under Bhim police station area, killing 25-year-old Priyanka Sharma on the spot, it said.
Priyanka's mother Urmila Sharma (58) and relative Ravi Kumar Sharma (22), who was driving the car, died during treatment at a hospital in Beawar town of Ajmer district, police said.
Ravi's father Gopal Sharma (50) also suffered injuries and was hospitalised, investigating officer in the case Suresh Dutt said.